diff --git a/agrest-engine/src/main/java/io/agrest/exp/parser/ExpAbs.java b/agrest-engine/src/main/java/io/agrest/exp/parser/ExpAbs.java
index b9a8a98d1..f327a1383 100644
--- a/agrest-engine/src/main/java/io/agrest/exp/parser/ExpAbs.java
+++ b/agrest-engine/src/main/java/io/agrest/exp/parser/ExpAbs.java
@@ -30,7 +30,7 @@ protected SimpleNode shallowCopy() {
 
   @Override
   public String toString() {
-    return children != null ? "abs(" + children[0] + ")" : "abs(?)";
+    return ExpStringConverter.convert(this);
   }
 }
 /* JavaCC - OriginalChecksum=01d2266f2e2852f0cc30cb38133844d2 (do not edit this line) */
diff --git a/agrest-engine/src/main/java/io/agrest/exp/parser/ExpAdd.java b/agrest-engine/src/main/java/io/agrest/exp/parser/ExpAdd.java
index 0ebb049ec..a0f5eecb9 100644
--- a/agrest-engine/src/main/java/io/agrest/exp/parser/ExpAdd.java
+++ b/agrest-engine/src/main/java/io/agrest/exp/parser/ExpAdd.java
@@ -30,7 +30,7 @@ protected SimpleNode shallowCopy() {
 
   @Override
   public String toString() {
-    return children != null ? "(" + children[0] + ") + (" + children[1] + ")" : "? + ?";
+    return ExpStringConverter.convert(this);
   }
 }
 /* JavaCC - OriginalChecksum=67440c31da272c3cf98559aaecf49bc2 (do not edit this line) */
diff --git a/agrest-engine/src/main/java/io/agrest/exp/parser/ExpAnd.java b/agrest-engine/src/main/java/io/agrest/exp/parser/ExpAnd.java
index 76fec75b1..0cccd3a40 100644
--- a/agrest-engine/src/main/java/io/agrest/exp/parser/ExpAnd.java
+++ b/agrest-engine/src/main/java/io/agrest/exp/parser/ExpAnd.java
@@ -33,9 +33,7 @@ protected SimpleNode shallowCopy() {
 
   @Override
   public String toString() {
-    return children != null
-            ? Arrays.stream(children).map(String::valueOf).collect(Collectors.joining(") and (", "(", ")"))
-            : "? and ?";
+    return ExpStringConverter.convert(this);
   }
 }
 /* JavaCC - OriginalChecksum=8fe8825e52daaa8c28bda97ebce7e8ec (do not edit this line) */
diff --git a/agrest-engine/src/main/java/io/agrest/exp/parser/ExpBetween.java b/agrest-engine/src/main/java/io/agrest/exp/parser/ExpBetween.java
index bb4fa3b18..1d8141629 100644
--- a/agrest-engine/src/main/java/io/agrest/exp/parser/ExpBetween.java
+++ b/agrest-engine/src/main/java/io/agrest/exp/parser/ExpBetween.java
@@ -30,9 +30,7 @@ protected SimpleNode shallowCopy() {
 
   @Override
   public String toString() {
-    return children != null
-            ? children[0] + " between " + children[1] + " and " + children[2]
-            : "? between ? and ?";
+    return ExpStringConverter.convert(this);
   }
 }
 /* JavaCC - OriginalChecksum=c43b74b247f96290e1207f5b0fcef774 (do not edit this line) */
diff --git a/agrest-engine/src/main/java/io/agrest/exp/parser/ExpBitwiseAnd.java b/agrest-engine/src/main/java/io/agrest/exp/parser/ExpBitwiseAnd.java
index 08eaace53..5efa4e933 100644
--- a/agrest-engine/src/main/java/io/agrest/exp/parser/ExpBitwiseAnd.java
+++ b/agrest-engine/src/main/java/io/agrest/exp/parser/ExpBitwiseAnd.java
@@ -30,9 +30,7 @@ protected SimpleNode shallowCopy() {
 
   @Override
   public String toString() {
-    return children != null
-            ? "(" + children[0] + ") & (" + children[1] + ")"
-            : "? & ?";
+    return ExpStringConverter.convert(this);
   }
 }
 /* JavaCC - OriginalChecksum=114e39f3e98a01e9d633fb36f9cdc27e (do not edit this line) */
diff --git a/agrest-engine/src/main/java/io/agrest/exp/parser/ExpBitwiseLeftShift.java b/agrest-engine/src/main/java/io/agrest/exp/parser/ExpBitwiseLeftShift.java
index 501a70c31..6c73d30e0 100644
--- a/agrest-engine/src/main/java/io/agrest/exp/parser/ExpBitwiseLeftShift.java
+++ b/agrest-engine/src/main/java/io/agrest/exp/parser/ExpBitwiseLeftShift.java
@@ -30,9 +30,7 @@ protected SimpleNode shallowCopy() {
 
   @Override
   public String toString() {
-    return children != null
-            ? "(" + children[0] + ") << (" + children[1] + ")"
-            : "? << ?";
+    return ExpStringConverter.convert(this);
   }
 }
 /* JavaCC - OriginalChecksum=a6ef6adcc35a4fc93a897a3b9a1b6dfd (do not edit this line) */
diff --git a/agrest-engine/src/main/java/io/agrest/exp/parser/ExpBitwiseNot.java b/agrest-engine/src/main/java/io/agrest/exp/parser/ExpBitwiseNot.java
index 369c8d99c..727f62177 100644
--- a/agrest-engine/src/main/java/io/agrest/exp/parser/ExpBitwiseNot.java
+++ b/agrest-engine/src/main/java/io/agrest/exp/parser/ExpBitwiseNot.java
@@ -30,9 +30,7 @@ protected SimpleNode shallowCopy() {
 
   @Override
   public String toString() {
-    return children != null
-            ? "~(" + children[0] + ")"
-            : "~ ?";
+    return ExpStringConverter.convert(this);
   }
 }
 /* JavaCC - OriginalChecksum=19c490da33ec6688721f4959812e3984 (do not edit this line) */
diff --git a/agrest-engine/src/main/java/io/agrest/exp/parser/ExpBitwiseOr.java b/agrest-engine/src/main/java/io/agrest/exp/parser/ExpBitwiseOr.java
index d097fa831..46e91b934 100644
--- a/agrest-engine/src/main/java/io/agrest/exp/parser/ExpBitwiseOr.java
+++ b/agrest-engine/src/main/java/io/agrest/exp/parser/ExpBitwiseOr.java
@@ -30,9 +30,7 @@ protected SimpleNode shallowCopy() {
 
   @Override
   public String toString() {
-    return children != null
-            ? "(" + children[0] + ") | (" + children[1] + ")"
-            : "? | ?";
+    return ExpStringConverter.convert(this);
   }
 }
 /* JavaCC - OriginalChecksum=9e655d2e49f2f89cbfc0290e3c55eaaa (do not edit this line) */
diff --git a/agrest-engine/src/main/java/io/agrest/exp/parser/ExpBitwiseRightShift.java b/agrest-engine/src/main/java/io/agrest/exp/parser/ExpBitwiseRightShift.java
index fa0491b27..5abb3af71 100644
--- a/agrest-engine/src/main/java/io/agrest/exp/parser/ExpBitwiseRightShift.java
+++ b/agrest-engine/src/main/java/io/agrest/exp/parser/ExpBitwiseRightShift.java
@@ -30,9 +30,7 @@ protected SimpleNode shallowCopy() {
 
   @Override
   public String toString() {
-    return children != null
-            ? "(" + children[0] + ") >> (" + children[1] + ")"
-            : "? >> ?";
+    return ExpStringConverter.convert(this);
   }
 }
 /* JavaCC - OriginalChecksum=a94a42dfe873885efa22739e3c810a38 (do not edit this line) */
diff --git a/agrest-engine/src/main/java/io/agrest/exp/parser/ExpBitwiseXor.java b/agrest-engine/src/main/java/io/agrest/exp/parser/ExpBitwiseXor.java
index a59e5332d..1aa954bf4 100644
--- a/agrest-engine/src/main/java/io/agrest/exp/parser/ExpBitwiseXor.java
+++ b/agrest-engine/src/main/java/io/agrest/exp/parser/ExpBitwiseXor.java
@@ -30,9 +30,7 @@ protected SimpleNode shallowCopy() {
 
   @Override
   public String toString() {
-    return children != null
-            ? "(" + children[0] + ") ^ (" + children[1] + ")"
-            : "? ^ ?";
+    return ExpStringConverter.convert(this);
   }
 }
 /* JavaCC - OriginalChecksum=9e28b3f45bea0aa6bcbfd7fa8910fd4e (do not edit this line) */
diff --git a/agrest-engine/src/main/java/io/agrest/exp/parser/ExpConcat.java b/agrest-engine/src/main/java/io/agrest/exp/parser/ExpConcat.java
index 1455c4b4d..52546b1bb 100644
--- a/agrest-engine/src/main/java/io/agrest/exp/parser/ExpConcat.java
+++ b/agrest-engine/src/main/java/io/agrest/exp/parser/ExpConcat.java
@@ -30,9 +30,7 @@ protected SimpleNode shallowCopy() {
 
   @Override
   public String toString() {
-    return children != null
-            ? "concat(" + children[0] + ", " + children[1] + ")"
-            : "concat(?, ?)";
+    return ExpStringConverter.convert(this);
   }
 }
 /* JavaCC - OriginalChecksum=2de2c03e3db046b2f2cdd50df8e4a48e (do not edit this line) */
diff --git a/agrest-engine/src/main/java/io/agrest/exp/parser/ExpCurrentDate.java b/agrest-engine/src/main/java/io/agrest/exp/parser/ExpCurrentDate.java
index 08e594216..df70513b8 100644
--- a/agrest-engine/src/main/java/io/agrest/exp/parser/ExpCurrentDate.java
+++ b/agrest-engine/src/main/java/io/agrest/exp/parser/ExpCurrentDate.java
@@ -30,7 +30,7 @@ protected SimpleNode shallowCopy() {
 
   @Override
   public String toString() {
-    return "currentDate()";
+    return ExpStringConverter.convert(this);
   }
 }
 /* JavaCC - OriginalChecksum=e13391251cba769cc41551502e16e0ac (do not edit this line) */
diff --git a/agrest-engine/src/main/java/io/agrest/exp/parser/ExpCurrentTime.java b/agrest-engine/src/main/java/io/agrest/exp/parser/ExpCurrentTime.java
index 2ccfea343..3becdd6c1 100644
--- a/agrest-engine/src/main/java/io/agrest/exp/parser/ExpCurrentTime.java
+++ b/agrest-engine/src/main/java/io/agrest/exp/parser/ExpCurrentTime.java
@@ -30,7 +30,7 @@ protected SimpleNode shallowCopy() {
 
   @Override
   public String toString() {
-    return "currentTime()";
+    return ExpStringConverter.convert(this);
   }
 }
 /* JavaCC - OriginalChecksum=1f84b3754ed74e9ae5b7eca31d84f0ae (do not edit this line) */
diff --git a/agrest-engine/src/main/java/io/agrest/exp/parser/ExpCurrentTimestamp.java b/agrest-engine/src/main/java/io/agrest/exp/parser/ExpCurrentTimestamp.java
index a7da6c55a..1661ccde8 100644
--- a/agrest-engine/src/main/java/io/agrest/exp/parser/ExpCurrentTimestamp.java
+++ b/agrest-engine/src/main/java/io/agrest/exp/parser/ExpCurrentTimestamp.java
@@ -30,7 +30,7 @@ protected ExpCurrentTimestamp shallowCopy() {
 
   @Override
   public String toString() {
-    return "currentTimestamp()";
+    return ExpStringConverter.convert(this);
   }
 }
 /* JavaCC - OriginalChecksum=c3ddadaa60478d01d051d9fd5b1f87c7 (do not edit this line) */
diff --git a/agrest-engine/src/main/java/io/agrest/exp/parser/ExpDivide.java b/agrest-engine/src/main/java/io/agrest/exp/parser/ExpDivide.java
index bbb457e2d..27e47d0b6 100644
--- a/agrest-engine/src/main/java/io/agrest/exp/parser/ExpDivide.java
+++ b/agrest-engine/src/main/java/io/agrest/exp/parser/ExpDivide.java
@@ -30,9 +30,7 @@ protected ExpDivide shallowCopy() {
 
   @Override
   public String toString() {
-    return children != null
-            ? "(" + children[0] + ") / (" + children[1] + ")"
-            : "? / ?";
+    return ExpStringConverter.convert(this);
   }
 }
 /* JavaCC - OriginalChecksum=ff843f7912488202daf5cfaf1517956b (do not edit this line) */
diff --git a/agrest-engine/src/main/java/io/agrest/exp/parser/ExpEqual.java b/agrest-engine/src/main/java/io/agrest/exp/parser/ExpEqual.java
index b83b881ac..9619af683 100644
--- a/agrest-engine/src/main/java/io/agrest/exp/parser/ExpEqual.java
+++ b/agrest-engine/src/main/java/io/agrest/exp/parser/ExpEqual.java
@@ -30,9 +30,7 @@ protected ExpEqual shallowCopy() {
 
   @Override
   public String toString() {
-    return children != null
-            ? "(" + children[0] + ") = (" + children[1] + ")"
-            : "? = ?";
+    return ExpStringConverter.convert(this);
   }
 }
 /* JavaCC - OriginalChecksum=5d0a19fd37d62fae2718cc73973efde7 (do not edit this line) */
diff --git a/agrest-engine/src/main/java/io/agrest/exp/parser/ExpExtract.java b/agrest-engine/src/main/java/io/agrest/exp/parser/ExpExtract.java
index ae53d7e2c..9286a7b1b 100644
--- a/agrest-engine/src/main/java/io/agrest/exp/parser/ExpExtract.java
+++ b/agrest-engine/src/main/java/io/agrest/exp/parser/ExpExtract.java
@@ -30,9 +30,7 @@ protected ExpExtract shallowCopy() {
 
   @Override
   public String toString() {
-    return children != null
-            ? value + "(" + children[0] + ")"
-            : value + "(?)";
+    return ExpStringConverter.convert(this);
   }
 }
 /* JavaCC - OriginalChecksum=58cc7e1d25270e1d515170647eb54773 (do not edit this line) */
diff --git a/agrest-engine/src/main/java/io/agrest/exp/parser/ExpFalse.java b/agrest-engine/src/main/java/io/agrest/exp/parser/ExpFalse.java
index d75c52a0b..9d9e15ff5 100644
--- a/agrest-engine/src/main/java/io/agrest/exp/parser/ExpFalse.java
+++ b/agrest-engine/src/main/java/io/agrest/exp/parser/ExpFalse.java
@@ -30,7 +30,7 @@ protected ExpFalse shallowCopy() {
 
   @Override
   public String toString() {
-    return "false";
+    return ExpStringConverter.convert(this);
   }
 }
 /* JavaCC - OriginalChecksum=f5ab544d76028320b4b1dbb970751376 (do not edit this line) */
diff --git a/agrest-engine/src/main/java/io/agrest/exp/parser/ExpGreater.java b/agrest-engine/src/main/java/io/agrest/exp/parser/ExpGreater.java
index 4ea87fb92..e0b0ce5a4 100644
--- a/agrest-engine/src/main/java/io/agrest/exp/parser/ExpGreater.java
+++ b/agrest-engine/src/main/java/io/agrest/exp/parser/ExpGreater.java
@@ -30,9 +30,7 @@ protected ExpGreater shallowCopy() {
 
   @Override
   public String toString() {
-    return children != null
-            ? "(" + children[0] + ") > (" + children[1] + ")"
-            : "? > ?";
+    return ExpStringConverter.convert(this);
   }
 }
 /* JavaCC - OriginalChecksum=ea0ce31b9d9db21857900434d14bd004 (do not edit this line) */
diff --git a/agrest-engine/src/main/java/io/agrest/exp/parser/ExpGreaterOrEqual.java b/agrest-engine/src/main/java/io/agrest/exp/parser/ExpGreaterOrEqual.java
index e641d5509..48d74361b 100644
--- a/agrest-engine/src/main/java/io/agrest/exp/parser/ExpGreaterOrEqual.java
+++ b/agrest-engine/src/main/java/io/agrest/exp/parser/ExpGreaterOrEqual.java
@@ -30,9 +30,7 @@ protected ExpGreaterOrEqual shallowCopy() {
 
   @Override
   public String toString() {
-    return children != null
-            ? "(" + children[0] + ") >= (" + children[1] + ")"
-            : "? >= ?";
+    return ExpStringConverter.convert(this);
   }
 }
 /* JavaCC - OriginalChecksum=723bcd56cadc1762fd2460f1ab9c988f (do not edit this line) */
diff --git a/agrest-engine/src/main/java/io/agrest/exp/parser/ExpIn.java b/agrest-engine/src/main/java/io/agrest/exp/parser/ExpIn.java
index b52f58e75..56916ab08 100644
--- a/agrest-engine/src/main/java/io/agrest/exp/parser/ExpIn.java
+++ b/agrest-engine/src/main/java/io/agrest/exp/parser/ExpIn.java
@@ -30,9 +30,7 @@ protected SimpleNode shallowCopy() {
 
   @Override
   public String toString() {
-    return children != null
-            ? children[0] + " in " + (children[1] instanceof ExpNamedParameter ? children[1] : "(" + children[1] + ")")
-            : "? in (?)";
+    return ExpStringConverter.convert(this);
   }
 }
 /* JavaCC - OriginalChecksum=40738702f4699c9b3a308d49a792f974 (do not edit this line) */
diff --git a/agrest-engine/src/main/java/io/agrest/exp/parser/ExpLength.java b/agrest-engine/src/main/java/io/agrest/exp/parser/ExpLength.java
index f969932ba..54f26e1a1 100644
--- a/agrest-engine/src/main/java/io/agrest/exp/parser/ExpLength.java
+++ b/agrest-engine/src/main/java/io/agrest/exp/parser/ExpLength.java
@@ -30,9 +30,7 @@ protected SimpleNode shallowCopy() {
 
   @Override
   public String toString() {
-    return children != null
-            ? "length(" + children[0] + ")"
-            : "length(?)";
+    return ExpStringConverter.convert(this);
   }
 }
 /* JavaCC - OriginalChecksum=f19b92880659daa8634dd190871429c4 (do not edit this line) */
diff --git a/agrest-engine/src/main/java/io/agrest/exp/parser/ExpLess.java b/agrest-engine/src/main/java/io/agrest/exp/parser/ExpLess.java
index 7b2b6dab9..151fd6c7c 100644
--- a/agrest-engine/src/main/java/io/agrest/exp/parser/ExpLess.java
+++ b/agrest-engine/src/main/java/io/agrest/exp/parser/ExpLess.java
@@ -30,9 +30,7 @@ protected SimpleNode shallowCopy() {
 
   @Override
   public String toString() {
-    return children != null
-            ? "(" + children[0] + ") < (" + children[1] + ")"
-            : "? < ?";
+    return ExpStringConverter.convert(this);
   }
 }
 /* JavaCC - OriginalChecksum=cd3543ed8cbdcb8d8a299d020cc92831 (do not edit this line) */
diff --git a/agrest-engine/src/main/java/io/agrest/exp/parser/ExpLessOrEqual.java b/agrest-engine/src/main/java/io/agrest/exp/parser/ExpLessOrEqual.java
index fcdc132e2..5a302dfcd 100644
--- a/agrest-engine/src/main/java/io/agrest/exp/parser/ExpLessOrEqual.java
+++ b/agrest-engine/src/main/java/io/agrest/exp/parser/ExpLessOrEqual.java
@@ -30,9 +30,7 @@ protected SimpleNode shallowCopy() {
 
   @Override
   public String toString() {
-    return children != null
-            ? "(" + children[0] + ") <= (" + children[1] + ")"
-            : "? <= ?";
+    return ExpStringConverter.convert(this);
   }
 }
 /* JavaCC - OriginalChecksum=0c80f493512f3c5d984682c830f7d9f1 (do not edit this line) */
diff --git a/agrest-engine/src/main/java/io/agrest/exp/parser/ExpLike.java b/agrest-engine/src/main/java/io/agrest/exp/parser/ExpLike.java
index c17b9f7c8..1893c1919 100644
--- a/agrest-engine/src/main/java/io/agrest/exp/parser/ExpLike.java
+++ b/agrest-engine/src/main/java/io/agrest/exp/parser/ExpLike.java
@@ -30,9 +30,7 @@ protected SimpleNode shallowCopy() {
 
   @Override
   public String toString() {
-    return children != null
-            ? children[0] + " like " + children[1] + (children.length > 2 ? " escape " + children[2] : "")
-            : "? like ?";
+    return ExpStringConverter.convert(this);
   }
 }
 /* JavaCC - OriginalChecksum=3985611ab5ab3bf8b4211521f95869c3 (do not edit this line) */
diff --git a/agrest-engine/src/main/java/io/agrest/exp/parser/ExpLikeIgnoreCase.java b/agrest-engine/src/main/java/io/agrest/exp/parser/ExpLikeIgnoreCase.java
index c0000a180..fe9d37be5 100644
--- a/agrest-engine/src/main/java/io/agrest/exp/parser/ExpLikeIgnoreCase.java
+++ b/agrest-engine/src/main/java/io/agrest/exp/parser/ExpLikeIgnoreCase.java
@@ -30,9 +30,7 @@ protected SimpleNode shallowCopy() {
 
   @Override
   public String toString() {
-    return children != null
-            ? children[0] + " likeIgnoreCase " + children[1] + (children.length > 2 ? " escape " + children[2] : "")
-            : "? likeIgnoreCase ?";
+    return ExpStringConverter.convert(this);
   }
 }
 /* JavaCC - OriginalChecksum=5ac0a75518b771f310fb884e4b827b71 (do not edit this line) */
diff --git a/agrest-engine/src/main/java/io/agrest/exp/parser/ExpLocate.java b/agrest-engine/src/main/java/io/agrest/exp/parser/ExpLocate.java
index 3a9336c9c..36096145d 100644
--- a/agrest-engine/src/main/java/io/agrest/exp/parser/ExpLocate.java
+++ b/agrest-engine/src/main/java/io/agrest/exp/parser/ExpLocate.java
@@ -30,9 +30,7 @@ protected SimpleNode shallowCopy() {
 
   @Override
   public String toString() {
-    return children != null
-            ? "locate(" + children[0] + ", " + children[1] + (children.length > 2 ? ", (" + children[2] + ")" : "") + ")"
-            : "locate(?, ?)";
+    return ExpStringConverter.convert(this);
   }
 }
 /* JavaCC - OriginalChecksum=f84e448f9a20bd2e9cfcd100ef030c8a (do not edit this line) */
diff --git a/agrest-engine/src/main/java/io/agrest/exp/parser/ExpLower.java b/agrest-engine/src/main/java/io/agrest/exp/parser/ExpLower.java
index 096379a4a..e2193999c 100644
--- a/agrest-engine/src/main/java/io/agrest/exp/parser/ExpLower.java
+++ b/agrest-engine/src/main/java/io/agrest/exp/parser/ExpLower.java
@@ -30,9 +30,7 @@ protected SimpleNode shallowCopy() {
 
   @Override
   public String toString() {
-    return children != null
-            ? "lower(" + children[0] + ")"
-            : "lower(?)";
+    return ExpStringConverter.convert(this);
   }
 }
 /* JavaCC - OriginalChecksum=46a8609164b2bd56451f930c7b2db122 (do not edit this line) */
diff --git a/agrest-engine/src/main/java/io/agrest/exp/parser/ExpMod.java b/agrest-engine/src/main/java/io/agrest/exp/parser/ExpMod.java
index 882c6e825..57f7a6b62 100644
--- a/agrest-engine/src/main/java/io/agrest/exp/parser/ExpMod.java
+++ b/agrest-engine/src/main/java/io/agrest/exp/parser/ExpMod.java
@@ -32,9 +32,7 @@ protected SimpleNode shallowCopy() {
 
     @Override
     public String toString() {
-        return children != null
-                ? "mod(" + children[0] + ", " + children[1] + ")"
-                : "mod(?, ?)";
+        return ExpStringConverter.convert(this);
     }
 }
 /* JavaCC - OriginalChecksum=6563b330904d626ec86b2bd306259dd3 (do not edit this line) */
diff --git a/agrest-engine/src/main/java/io/agrest/exp/parser/ExpMultiply.java b/agrest-engine/src/main/java/io/agrest/exp/parser/ExpMultiply.java
index 9304ad039..f80f44a4f 100644
--- a/agrest-engine/src/main/java/io/agrest/exp/parser/ExpMultiply.java
+++ b/agrest-engine/src/main/java/io/agrest/exp/parser/ExpMultiply.java
@@ -30,9 +30,7 @@ protected SimpleNode shallowCopy() {
 
   @Override
   public String toString() {
-    return children != null
-            ? "(" + children[0] + ") * (" + children[1] + ")"
-            : "? * ?";
+    return ExpStringConverter.convert(this);
   }
 }
 /* JavaCC - OriginalChecksum=6ca0df20d086adb54be14cd41b93ed59 (do not edit this line) */
diff --git a/agrest-engine/src/main/java/io/agrest/exp/parser/ExpNamedParameter.java b/agrest-engine/src/main/java/io/agrest/exp/parser/ExpNamedParameter.java
index 615e924a1..0e36390e0 100644
--- a/agrest-engine/src/main/java/io/agrest/exp/parser/ExpNamedParameter.java
+++ b/agrest-engine/src/main/java/io/agrest/exp/parser/ExpNamedParameter.java
@@ -50,10 +50,9 @@ protected SimpleNode shallowCopy() {
     return copy;
   }
 
-    @Override
-    public String toString() {
-        String name = getName();
-        return name != null ? "$" + name : "null";
-    }
+  @Override
+  public String toString() {
+    return ExpStringConverter.convert(this);
+  }
 }
 /* JavaCC - OriginalChecksum=7b4e7b4225063fe3b24686d5b6a2ada2 (do not edit this line) */
diff --git a/agrest-engine/src/main/java/io/agrest/exp/parser/ExpNegate.java b/agrest-engine/src/main/java/io/agrest/exp/parser/ExpNegate.java
index 25eb71437..decff17ec 100644
--- a/agrest-engine/src/main/java/io/agrest/exp/parser/ExpNegate.java
+++ b/agrest-engine/src/main/java/io/agrest/exp/parser/ExpNegate.java
@@ -30,9 +30,7 @@ protected SimpleNode shallowCopy() {
 
   @Override
   public String toString() {
-    return children != null
-            ? "-(" + children[0] + ")"
-            : "-?";
+    return ExpStringConverter.convert(this);
   }
 }
 /* JavaCC - OriginalChecksum=100942f12f6576bdafd2b6051325e733 (do not edit this line) */
diff --git a/agrest-engine/src/main/java/io/agrest/exp/parser/ExpNot.java b/agrest-engine/src/main/java/io/agrest/exp/parser/ExpNot.java
index 2c752e839..a23f72425 100644
--- a/agrest-engine/src/main/java/io/agrest/exp/parser/ExpNot.java
+++ b/agrest-engine/src/main/java/io/agrest/exp/parser/ExpNot.java
@@ -37,9 +37,7 @@ public Exp not() {
 
   @Override
   public String toString() {
-    return children != null
-            ? "not (" + children[0] + ")"
-            : "not ?";
+    return ExpStringConverter.convert(this);
   }
 }
 /* JavaCC - OriginalChecksum=0fe2b3f475a020609f2cfa348e9fe03d (do not edit this line) */
diff --git a/agrest-engine/src/main/java/io/agrest/exp/parser/ExpNotBetween.java b/agrest-engine/src/main/java/io/agrest/exp/parser/ExpNotBetween.java
index 3848ad66c..f4ec4f0e5 100644
--- a/agrest-engine/src/main/java/io/agrest/exp/parser/ExpNotBetween.java
+++ b/agrest-engine/src/main/java/io/agrest/exp/parser/ExpNotBetween.java
@@ -32,9 +32,7 @@ protected ExpNotBetween shallowCopy() {
 
   @Override
   public String toString() {
-    return children != null
-            ? children[0] + " not between " + children[1] + " and " + children[2]
-            : "? not between ? and ?";
+    return ExpStringConverter.convert(this);
   }
 }
 /* JavaCC - OriginalChecksum=1af9c63e271dbd73a0ef825dda231d68 (do not edit this line) */
diff --git a/agrest-engine/src/main/java/io/agrest/exp/parser/ExpNotEqual.java b/agrest-engine/src/main/java/io/agrest/exp/parser/ExpNotEqual.java
index c83dc3e51..b738c2cf7 100644
--- a/agrest-engine/src/main/java/io/agrest/exp/parser/ExpNotEqual.java
+++ b/agrest-engine/src/main/java/io/agrest/exp/parser/ExpNotEqual.java
@@ -32,9 +32,7 @@ protected ExpNotEqual shallowCopy() {
 
   @Override
   public String toString() {
-    return children != null
-            ? "(" + children[0] + ") != (" + children[1] + ")"
-            : "? != ?";
+    return ExpStringConverter.convert(this);
   }
 }
 /* JavaCC - OriginalChecksum=cd31a8834ec599e6eb06535df7a2b157 (do not edit this line) */
diff --git a/agrest-engine/src/main/java/io/agrest/exp/parser/ExpNotIn.java b/agrest-engine/src/main/java/io/agrest/exp/parser/ExpNotIn.java
index 4ed0ce5d5..a7937efbc 100644
--- a/agrest-engine/src/main/java/io/agrest/exp/parser/ExpNotIn.java
+++ b/agrest-engine/src/main/java/io/agrest/exp/parser/ExpNotIn.java
@@ -32,9 +32,7 @@ protected ExpNotIn shallowCopy() {
 
   @Override
   public String toString() {
-    return children != null
-            ? children[0] + " not in " + (children[1].getClass() == ExpNamedParameter.class ? children[1] : "(" + children[1] + ")")
-            : "? not in (?)";
+    return ExpStringConverter.convert(this);
   }
 }
 /* JavaCC - OriginalChecksum=49ec5ffe4a961c9a3e6170dbd0f7ad1f (do not edit this line) */
diff --git a/agrest-engine/src/main/java/io/agrest/exp/parser/ExpNotLike.java b/agrest-engine/src/main/java/io/agrest/exp/parser/ExpNotLike.java
index d851d1da3..a0dd0e0b5 100644
--- a/agrest-engine/src/main/java/io/agrest/exp/parser/ExpNotLike.java
+++ b/agrest-engine/src/main/java/io/agrest/exp/parser/ExpNotLike.java
@@ -32,9 +32,7 @@ protected ExpNotLike shallowCopy() {
 
   @Override
   public String toString() {
-    return children != null
-            ? children[0] + " not like " + children[1] + (children.length > 2 ? " escape " + children[2] : "")
-            : "? not like ?";
+    return ExpStringConverter.convert(this);
   }
 }
 /* JavaCC - OriginalChecksum=9551a6b7ade4165e58bcc54093cfb9dd (do not edit this line) */
diff --git a/agrest-engine/src/main/java/io/agrest/exp/parser/ExpNotLikeIgnoreCase.java b/agrest-engine/src/main/java/io/agrest/exp/parser/ExpNotLikeIgnoreCase.java
index 1b5cef244..674fba14f 100644
--- a/agrest-engine/src/main/java/io/agrest/exp/parser/ExpNotLikeIgnoreCase.java
+++ b/agrest-engine/src/main/java/io/agrest/exp/parser/ExpNotLikeIgnoreCase.java
@@ -32,9 +32,7 @@ protected ExpNotLikeIgnoreCase shallowCopy() {
 
   @Override
   public String toString() {
-    return children != null
-            ? children[0] + " not likeIgnoreCase " + children[1] + (children.length > 2 ? " escape " + children[2] : "")
-            : "? not likeIgnoreCase ?";
+    return ExpStringConverter.convert(this);
   }
 }
 /* JavaCC - OriginalChecksum=d8fe9f940e276eee5cebf87aaffb7afb (do not edit this line) */
diff --git a/agrest-engine/src/main/java/io/agrest/exp/parser/ExpOr.java b/agrest-engine/src/main/java/io/agrest/exp/parser/ExpOr.java
index 3cf38bfc5..da2c7360d 100644
--- a/agrest-engine/src/main/java/io/agrest/exp/parser/ExpOr.java
+++ b/agrest-engine/src/main/java/io/agrest/exp/parser/ExpOr.java
@@ -33,9 +33,7 @@ protected ExpOr shallowCopy() {
 
   @Override
   public String toString() {
-    return children != null
-            ? Arrays.stream(children).map(String::valueOf).collect(Collectors.joining(") or (", "(", ")"))
-            : "? or ?";
+    return ExpStringConverter.convert(this);
   }
 }
 /* JavaCC - OriginalChecksum=674a058bd6a706248aae7d6f4cb49ef6 (do not edit this line) */
diff --git a/agrest-engine/src/main/java/io/agrest/exp/parser/ExpPath.java b/agrest-engine/src/main/java/io/agrest/exp/parser/ExpPath.java
index e1185a81e..e90939e8f 100644
--- a/agrest-engine/src/main/java/io/agrest/exp/parser/ExpPath.java
+++ b/agrest-engine/src/main/java/io/agrest/exp/parser/ExpPath.java
@@ -61,7 +61,7 @@ public int hashCode() {
 
   @Override
   public String toString() {
-    return String.valueOf(value);
+    return ExpStringConverter.convert(this);
   }
 }
 /* JavaCC - OriginalChecksum=ffcf3b869e9e5d281a4b47d7ac3ebd15 (do not edit this line) */
diff --git a/agrest-engine/src/main/java/io/agrest/exp/parser/ExpScalar.java b/agrest-engine/src/main/java/io/agrest/exp/parser/ExpScalar.java
index 2625888ba..9db0c6b35 100644
--- a/agrest-engine/src/main/java/io/agrest/exp/parser/ExpScalar.java
+++ b/agrest-engine/src/main/java/io/agrest/exp/parser/ExpScalar.java
@@ -42,11 +42,7 @@ protected ExpScalar shallowCopy() {
 
     @Override
     public String toString() {
-        if (value instanceof CharSequence) {
-            return "'" + value + "'";
-        } else {
-            return String.valueOf(value);
-        }
+        return ExpStringConverter.convert(this);
     }
 }
 /* JavaCC - OriginalChecksum=21004db13a44c6b16cc9797a6f36a4af (do not edit this line) */
diff --git a/agrest-engine/src/main/java/io/agrest/exp/parser/ExpScalarList.java b/agrest-engine/src/main/java/io/agrest/exp/parser/ExpScalarList.java
index 9025df7e1..2344b43ce 100644
--- a/agrest-engine/src/main/java/io/agrest/exp/parser/ExpScalarList.java
+++ b/agrest-engine/src/main/java/io/agrest/exp/parser/ExpScalarList.java
@@ -69,11 +69,7 @@ protected ExpScalarList shallowCopy() {
 
   @Override
   public String toString() {
-      // children can be either an internal collection, or child nodes, so must use "getValue()"
-      return getValue()
-              .stream()
-              .map(v -> v instanceof CharSequence ? "'" + v + "'" : String.valueOf(v))
-              .collect(Collectors.joining(", "));
+    return ExpStringConverter.convert(this);
   }
 
   private static class ListValueVisitor extends AgExpressionParserDefaultVisitor<List<Object>> {
diff --git a/agrest-engine/src/main/java/io/agrest/exp/parser/ExpSqrt.java b/agrest-engine/src/main/java/io/agrest/exp/parser/ExpSqrt.java
index 52b28d38f..1f2c748af 100644
--- a/agrest-engine/src/main/java/io/agrest/exp/parser/ExpSqrt.java
+++ b/agrest-engine/src/main/java/io/agrest/exp/parser/ExpSqrt.java
@@ -31,7 +31,7 @@ protected ExpSqrt shallowCopy() {
 
   @Override
   public String toString() {
-    return children != null ? "sqrt(" + children[0] + ")" : "sqrt(?)";
+    return ExpStringConverter.convert(this);
   }
 }
 /* JavaCC - OriginalChecksum=e749d50dc99d6d7acc161593f5e1b43e (do not edit this line) */
diff --git a/agrest-engine/src/main/java/io/agrest/exp/parser/ExpStringConverter.java b/agrest-engine/src/main/java/io/agrest/exp/parser/ExpStringConverter.java
new file mode 100644
index 000000000..f637e93b8
--- /dev/null
+++ b/agrest-engine/src/main/java/io/agrest/exp/parser/ExpStringConverter.java
@@ -0,0 +1,312 @@
+package io.agrest.exp.parser;
+
+import io.agrest.protocol.Exp;
+
+import java.util.Arrays;
+import java.util.HashSet;
+import java.util.List;
+import java.util.Set;
+import java.util.stream.Collectors;
+
+public final class ExpStringConverter {
+
+    private static final Set<Class<? extends Exp>> parenthesesUnnecessaryExps = Set.of(
+            ExpAbs.class,
+            ExpCurrentDate.class,
+            ExpCurrentTime.class,
+            ExpCurrentTimestamp.class,
+            ExpExtract.class,
+            ExpFalse.class,
+            ExpLength.class,
+            ExpLocate.class,
+            ExpLower.class,
+            ExpNamedParameter.class,
+            ExpPath.class,
+            ExpScalar.class,
+            ExpSqrt.class,
+            ExpSubstring.class,
+            ExpTrim.class,
+            ExpTrue.class,
+            ExpUpper.class
+    );
+
+    private ExpStringConverter() {
+    }
+
+    public static String convert(ExpAbs exp) {
+        return exp.children != null ? "abs(" + exp.children[0] + ")" : "abs(?)";
+    }
+
+    public static String convert(ExpAdd exp) {
+        return exp.children != null
+                ? tryParenthesize(exp.children[0]) + " + " + tryParenthesize(exp.children[1])
+                : "? + ?";
+    }
+
+    public static String convert(ExpAnd exp) {
+        return exp.children != null
+                ? Arrays.stream(exp.children)
+                .map(ExpStringConverter::tryParenthesize)
+                .collect(Collectors.joining(" and "))
+                : "? and ?";
+    }
+
+    public static String convert(ExpBetween exp) {
+        return exp.children != null
+                ? exp.children[0] + " between " + exp.children[1] + " and " + exp.children[2]
+                : "? between ? and ?";
+    }
+
+    public static String convert(ExpBitwiseAnd exp) {
+        return exp.children != null
+                ? tryParenthesize(exp.children[0]) + " & " + tryParenthesize(exp.children[1])
+                : "? & ?";
+    }
+
+    public static String convert(ExpBitwiseLeftShift exp) {
+        return exp.children != null
+                ? tryParenthesize(exp.children[0]) + " << " + tryParenthesize(exp.children[1])
+                : "? << ?";
+    }
+
+    public static String convert(ExpBitwiseNot exp) {
+        return exp.children != null
+                ? "~" + tryParenthesize(exp.children[0])
+                : "~ ?";
+    }
+
+    public static String convert(ExpBitwiseOr exp) {
+        return exp.children != null
+                ? tryParenthesize(exp.children[0]) + " | " + tryParenthesize(exp.children[1])
+                : "? | ?";
+    }
+
+    public static String convert(ExpBitwiseRightShift exp) {
+        return exp.children != null
+                ? tryParenthesize(exp.children[0]) + " >> " + tryParenthesize(exp.children[1])
+                : "? >> ?";
+    }
+
+    public static String convert(ExpBitwiseXor exp) {
+        return exp.children != null
+                ? tryParenthesize(exp.children[0]) + " ^ " + tryParenthesize(exp.children[1])
+                : "? ^ ?";
+    }
+
+    public static String convert(ExpConcat exp) {
+        return "concat(" + (exp.children != null ? exp.children[0] + ", " + exp.children[1] : "?, ?") + ")";
+    }
+
+    @SuppressWarnings("unused")
+    public static String convert(ExpCurrentDate exp) {
+        return "currentDate()";
+    }
+
+    @SuppressWarnings("unused")
+    public static String convert(ExpCurrentTime exp) {
+        return "currentTime()";
+    }
+
+    @SuppressWarnings("unused")
+    public static String convert(ExpCurrentTimestamp exp) {
+        return "currentTimestamp()";
+    }
+
+    public static String convert(ExpDivide exp) {
+        return exp.children != null
+                ? tryParenthesize(exp.children[0]) + " / " + tryParenthesize(exp.children[1])
+                : "? / ?";
+    }
+
+    public static String convert(ExpEqual exp) {
+        return exp.children != null
+                ? tryParenthesize(exp.children[0]) + " = " + tryParenthesize(exp.children[1])
+                : "? = ?";
+    }
+
+    public static String convert(ExpExtract exp) {
+        return exp.children != null
+                ? exp.value + "(" + exp.children[0] + ")"
+                : exp.value + "(?)";
+    }
+
+    @SuppressWarnings("unused")
+    public static String convert(ExpFalse exp) {
+        return "false";
+    }
+
+    public static String convert(ExpGreater exp) {
+        return exp.children != null
+                ? tryParenthesize(exp.children[0]) + " > " + tryParenthesize(exp.children[1])
+                : "? > ?";
+    }
+
+    public static String convert(ExpGreaterOrEqual exp) {
+        return exp.children != null
+                ? tryParenthesize(exp.children[0]) + " >= " + tryParenthesize(exp.children[1])
+                : "? >= ?";
+    }
+
+    public static String convert(ExpIn exp) {
+        return exp.children != null
+                ? exp.children[0] + " in " + (exp.children[1] instanceof ExpNamedParameter ? exp.children[1] : "(" + exp.children[1] + ")")
+                : "? in (?)";
+    }
+
+    public static String convert(ExpLength exp) {
+        return "length(" + (exp.children != null ? exp.children[0] : "?") + ")";
+    }
+
+    public static String convert(ExpLess exp) {
+        return exp.children != null
+                ? tryParenthesize(exp.children[0]) + " < " + tryParenthesize(exp.children[1])
+                : "? < ?";
+    }
+
+    public static String convert(ExpLessOrEqual exp) {
+        return exp.children != null
+                ? tryParenthesize(exp.children[0]) + " <= " + tryParenthesize(exp.children[1])
+                : "? <= ?";
+    }
+
+    public static String convert(ExpLike exp) {
+        return exp.children != null
+                ? exp.children[0] + " like " + exp.children[1] + (exp.children.length > 2 ? " escape " + exp.children[2] : "")
+                : "? like ?";
+    }
+
+    public static String convert(ExpLikeIgnoreCase exp) {
+        return exp.children != null
+                ? exp.children[0] + " likeIgnoreCase " + exp.children[1] + (exp.children.length > 2 ? " escape " + exp.children[2] : "")
+                : "? likeIgnoreCase ?";
+    }
+
+    public static String convert(ExpLocate exp) {
+        return "locate(" + (exp.children != null
+                ? exp.children[0] + ", " + exp.children[1] + (exp.children.length > 2 ? ", (" + exp.children[2] + ")" : "")
+                : "?, ?"
+        ) + ")";
+    }
+
+    public static String convert(ExpLower exp) {
+        return "lower(" + (exp.children != null ? exp.children[0] : "?") + ")";
+    }
+
+    public static String convert(ExpMod exp) {
+        return "mod(" + (exp.children != null ? exp.children[0] + ", " + exp.children[1] : "?, ?") + ")";
+    }
+
+    public static String convert(ExpMultiply exp) {
+        return exp.children != null
+                ? tryParenthesize(exp.children[0]) + " * " + tryParenthesize(exp.children[1])
+                : "? * ?";
+    }
+
+    public static String convert(ExpNamedParameter exp) {
+        String name = exp.getName();
+        return name != null ? "$" + name : "?";
+    }
+
+    public static String convert(ExpNegate exp) {
+        return exp.children != null
+                ? "-" + tryParenthesize(exp.children[0])
+                : "-?";
+    }
+
+    public static String convert(ExpNot exp) {
+        return "not " + (exp.children != null ? tryParenthesize(exp.children[0]) : "?");
+    }
+
+    public static String convert(ExpNotBetween exp) {
+        return exp.children != null
+                ? exp.children[0] + " not between " + exp.children[1] + " and " + exp.children[2]
+                : "? not between ? and ?";
+    }
+
+    public static String convert(ExpNotEqual exp) {
+        return exp.children != null
+                ? tryParenthesize(exp.children[0]) + " != " + tryParenthesize(exp.children[1])
+                : "? != ?";
+    }
+
+    public static String convert(ExpNotIn exp) {
+        return exp.children != null
+                ? exp.children[0] + " not in " + (exp.children[1].getClass() == ExpNamedParameter.class ? exp.children[1] : "(" + exp.children[1] + ")")
+                : "? not in (?)";
+    }
+
+    public static String convert(ExpNotLike exp) {
+        return exp.children != null
+                ? exp.children[0] + " not like " + exp.children[1] + (exp.children.length > 2 ? " escape " + exp.children[2] : "")
+                : "? not like ?";
+    }
+
+    public static String convert(ExpNotLikeIgnoreCase exp) {
+        return exp.children != null
+                ? exp.children[0] + " not likeIgnoreCase " + exp.children[1] + (exp.children.length > 2 ? " escape " + exp.children[2] : "")
+                : "? not likeIgnoreCase ?";
+    }
+
+    public static String convert(ExpOr exp) {
+        return exp.children != null
+                ? Arrays.stream(exp.children)
+                .map(ExpStringConverter::tryParenthesize)
+                .collect(Collectors.joining(" or "))
+                : "? or ?";
+    }
+
+    public static String convert(ExpPath exp) {
+        return String.valueOf(exp.value);
+    }
+
+    public static String convert(ExpScalar exp) {
+        return exp.value instanceof CharSequence
+                ? "'" + exp.value + "'"
+                : String.valueOf(exp.value);
+    }
+
+    public static String convert(ExpScalarList exp) {
+        // children can be either an internal collection, or child nodes, so must use "getValue()"
+        return exp.getValue()
+                .stream()
+                .map(v -> v instanceof CharSequence ? "'" + v + "'" : String.valueOf(v))
+                .collect(Collectors.joining(", "));
+    }
+
+    public static String convert(ExpSqrt exp) {
+        return exp.children != null ? "sqrt(" + exp.children[0] + ")" : "sqrt(?)";
+    }
+
+    public static String convert(ExpSubstring exp) {
+        return "substring(" + (exp.children != null
+                ? exp.children[0] + ", " + exp.children[1] + (exp.children.length > 2 ? ", " + exp.children[2] : "")
+                : "?, ?"
+        ) + ")";
+    }
+
+    public static String convert(ExpSubtract exp) {
+        return exp.children != null
+                ? tryParenthesize(exp.children[0]) + " - " + tryParenthesize(exp.children[1])
+                : "? - ?";
+    }
+
+    public static String convert(ExpTrim exp) {
+        return "trim(" + (exp.children != null ? exp.children[0] : "?") + ")";
+    }
+
+    @SuppressWarnings("unused")
+    public static String convert(ExpTrue exp) {
+        return "true";
+    }
+
+    public static String convert(ExpUpper exp) {
+        return "upper(" + (exp.children != null ? exp.children[0] : "?") + ")";
+    }
+
+    private static String tryParenthesize(Object object) {
+        if (parenthesesUnnecessaryExps.contains(object.getClass())) {
+            return String.valueOf(object);
+        }
+        return "(" + object + ")";
+    }
+}
diff --git a/agrest-engine/src/main/java/io/agrest/exp/parser/ExpSubstring.java b/agrest-engine/src/main/java/io/agrest/exp/parser/ExpSubstring.java
index ce42e2b71..5e2cd4d87 100644
--- a/agrest-engine/src/main/java/io/agrest/exp/parser/ExpSubstring.java
+++ b/agrest-engine/src/main/java/io/agrest/exp/parser/ExpSubstring.java
@@ -31,9 +31,7 @@ protected ExpSubstring shallowCopy() {
 
   @Override
   public String toString() {
-    return children != null
-            ? "substring(" + children[0] + ", " + children[1] + (children.length > 2 ? ", " + children[2] : "") + ")"
-            : "substring(?, ?)";
+    return ExpStringConverter.convert(this);
   }
 }
 /* JavaCC - OriginalChecksum=b4242b007471c91ebcaa890a9eac531d (do not edit this line) */
diff --git a/agrest-engine/src/main/java/io/agrest/exp/parser/ExpSubtract.java b/agrest-engine/src/main/java/io/agrest/exp/parser/ExpSubtract.java
index c1085dd58..243638402 100644
--- a/agrest-engine/src/main/java/io/agrest/exp/parser/ExpSubtract.java
+++ b/agrest-engine/src/main/java/io/agrest/exp/parser/ExpSubtract.java
@@ -31,9 +31,7 @@ protected ExpSubtract shallowCopy() {
 
   @Override
   public String toString() {
-    return children != null
-            ? "(" + children[0] + ") - (" + children[1] + ")"
-            : "? - ?";
+    return ExpStringConverter.convert(this);
   }
 }
 /* JavaCC - OriginalChecksum=9461ebb6e8a7eebd514bd15e14ac0623 (do not edit this line) */
diff --git a/agrest-engine/src/main/java/io/agrest/exp/parser/ExpTrim.java b/agrest-engine/src/main/java/io/agrest/exp/parser/ExpTrim.java
index e7611b7cf..8e8ee9862 100644
--- a/agrest-engine/src/main/java/io/agrest/exp/parser/ExpTrim.java
+++ b/agrest-engine/src/main/java/io/agrest/exp/parser/ExpTrim.java
@@ -31,9 +31,7 @@ protected ExpTrim shallowCopy() {
 
   @Override
   public String toString() {
-    return children != null
-            ? "trim(" + children[0] + ")"
-            : "trim(?)";
+    return ExpStringConverter.convert(this);
   }
 }
 /* JavaCC - OriginalChecksum=ccfdd54aef305779d90fa4c832c4339a (do not edit this line) */
diff --git a/agrest-engine/src/main/java/io/agrest/exp/parser/ExpTrue.java b/agrest-engine/src/main/java/io/agrest/exp/parser/ExpTrue.java
index 0b978a4b6..624d6e300 100644
--- a/agrest-engine/src/main/java/io/agrest/exp/parser/ExpTrue.java
+++ b/agrest-engine/src/main/java/io/agrest/exp/parser/ExpTrue.java
@@ -31,7 +31,7 @@ protected ExpTrue shallowCopy() {
 
   @Override
   public String toString() {
-    return "true";
+    return ExpStringConverter.convert(this);
   }
 }
 /* JavaCC - OriginalChecksum=bffdc7c3290d2409a6389b3cea4985d3 (do not edit this line) */
diff --git a/agrest-engine/src/main/java/io/agrest/exp/parser/ExpUpper.java b/agrest-engine/src/main/java/io/agrest/exp/parser/ExpUpper.java
index 09a55938a..f8b92f6ba 100644
--- a/agrest-engine/src/main/java/io/agrest/exp/parser/ExpUpper.java
+++ b/agrest-engine/src/main/java/io/agrest/exp/parser/ExpUpper.java
@@ -31,9 +31,7 @@ protected ExpUpper shallowCopy() {
 
   @Override
   public String toString() {
-    return children != null
-            ? "upper(" + children[0] + ")"
-            : "upper(?)";
+    return ExpStringConverter.convert(this);
   }
 }
 /* JavaCC - OriginalChecksum=579bc67a9a18bf15184b23f2649cc451 (do not edit this line) */
diff --git a/agrest-engine/src/main/java/io/agrest/exp/parser/SimpleNode.java b/agrest-engine/src/main/java/io/agrest/exp/parser/SimpleNode.java
index 60fee601e..e0b0a2af3 100644
--- a/agrest-engine/src/main/java/io/agrest/exp/parser/SimpleNode.java
+++ b/agrest-engine/src/main/java/io/agrest/exp/parser/SimpleNode.java
@@ -280,7 +280,6 @@ public int hashCode() {
         result = 31 * result + Arrays.hashCode(children);
         return result;
     }
-
 }
 
 /* JavaCC - OriginalChecksum=5b582160ae0ddf8fccabd52a1f82953e (do not edit this line) */
diff --git a/agrest-engine/src/test/java/io/agrest/exp/parser/ExpAddTest.java b/agrest-engine/src/test/java/io/agrest/exp/parser/ExpAddTest.java
index b25ce6a0c..6777a69f2 100644
--- a/agrest-engine/src/test/java/io/agrest/exp/parser/ExpAddTest.java
+++ b/agrest-engine/src/test/java/io/agrest/exp/parser/ExpAddTest.java
@@ -27,8 +27,8 @@ public void parse(String expString) {
 
     @ParameterizedTest
     @CsvSource(delimiter = '|', value = {
-            "1+2|(1) + (2)",
-            "1 +  2|(1) + (2)"
+            "1+2|1 + 2",
+            "1 +  2|1 + 2"
     })
     public void parsedToString(String expString, String expected) {
         assertEquals(expected, Exp.parse(expString).toString());
diff --git a/agrest-engine/src/test/java/io/agrest/exp/parser/ExpAndTest.java b/agrest-engine/src/test/java/io/agrest/exp/parser/ExpAndTest.java
index 5af9142e9..13c4d56e2 100644
--- a/agrest-engine/src/test/java/io/agrest/exp/parser/ExpAndTest.java
+++ b/agrest-engine/src/test/java/io/agrest/exp/parser/ExpAndTest.java
@@ -29,10 +29,10 @@ public void parse(String expString) {
 
     @ParameterizedTest
     @CsvSource(delimiter = '|', value = {
-            "a and b|(a) and (b)",
-            "a and  b|(a) and (b)",
-            "a and b and c|(a) and (b) and (c)",
-            "(a or b) and (c or d)|((a) or (b)) and ((c) or (d))"
+            "a and b|a and b",
+            "a and  b|a and b",
+            "a and b and c|a and b and c",
+            "(a or b) and (c or d)|(a or b) and (c or d)"
     })
     public void parsedToString(String expString, String expected) {
         assertEquals(expected, Exp.parse(expString).toString());
diff --git a/agrest-engine/src/test/java/io/agrest/exp/parser/ExpBitwiseAndTest.java b/agrest-engine/src/test/java/io/agrest/exp/parser/ExpBitwiseAndTest.java
index d48c755a1..f01bfe079 100644
--- a/agrest-engine/src/test/java/io/agrest/exp/parser/ExpBitwiseAndTest.java
+++ b/agrest-engine/src/test/java/io/agrest/exp/parser/ExpBitwiseAndTest.java
@@ -25,8 +25,8 @@ public void parse(String expString) {
 
     @ParameterizedTest
     @CsvSource(delimiter = '|', value = {
-            "1&2|(1) & (2)",
-            "1 &  2|(1) & (2)"
+            "1&2|1 & 2",
+            "1 &  2|1 & 2"
     })
     public void parsedToString(String expString, String expected) {
         assertEquals(expected, Exp.parse(expString).toString());
diff --git a/agrest-engine/src/test/java/io/agrest/exp/parser/ExpBitwiseLeftShiftTest.java b/agrest-engine/src/test/java/io/agrest/exp/parser/ExpBitwiseLeftShiftTest.java
index 4754f456b..70243e237 100644
--- a/agrest-engine/src/test/java/io/agrest/exp/parser/ExpBitwiseLeftShiftTest.java
+++ b/agrest-engine/src/test/java/io/agrest/exp/parser/ExpBitwiseLeftShiftTest.java
@@ -26,8 +26,8 @@ void parse(String expString) {
 
     @ParameterizedTest
     @CsvSource(delimiter = '|', value = {
-            "1<<2|(1) << (2)",
-            "1 <<  2|(1) << (2)"
+            "1<<2|1 << 2",
+            "1 <<  2|1 << 2"
     })
     public void parsedToString(String expString, String expected) {
         assertEquals(expected, Exp.parse(expString).toString());
diff --git a/agrest-engine/src/test/java/io/agrest/exp/parser/ExpBitwiseNotTest.java b/agrest-engine/src/test/java/io/agrest/exp/parser/ExpBitwiseNotTest.java
index 9b7d4753f..f66f9fefe 100644
--- a/agrest-engine/src/test/java/io/agrest/exp/parser/ExpBitwiseNotTest.java
+++ b/agrest-engine/src/test/java/io/agrest/exp/parser/ExpBitwiseNotTest.java
@@ -26,8 +26,8 @@ void parse(String expString) {
 
     @ParameterizedTest
     @CsvSource(delimiter = '|', value = {
-            "~2|~(2)",
-            "~ 2|~(2)"
+            "~2|~2",
+            "~ 2|~2"
     })
     public void parsedToString(String expString, String expected) {
         assertEquals(expected, Exp.parse(expString).toString());
diff --git a/agrest-engine/src/test/java/io/agrest/exp/parser/ExpBitwiseOrTest.java b/agrest-engine/src/test/java/io/agrest/exp/parser/ExpBitwiseOrTest.java
index d3e0eda6e..98db0f82b 100644
--- a/agrest-engine/src/test/java/io/agrest/exp/parser/ExpBitwiseOrTest.java
+++ b/agrest-engine/src/test/java/io/agrest/exp/parser/ExpBitwiseOrTest.java
@@ -26,8 +26,8 @@ void parse(String expString) {
 
     @ParameterizedTest
     @CsvSource(delimiter = ':', value = {
-            "1|2:(1) | (2)",
-            "1 |  2:(1) | (2)"
+            "1|2:1 | 2",
+            "1 |  2:1 | 2"
     })
     public void parsedToString(String expString, String expected) {
         assertEquals(expected, Exp.parse(expString).toString());
diff --git a/agrest-engine/src/test/java/io/agrest/exp/parser/ExpBitwiseRightShiftTest.java b/agrest-engine/src/test/java/io/agrest/exp/parser/ExpBitwiseRightShiftTest.java
index df2c8c2d9..a6dbd9dd0 100644
--- a/agrest-engine/src/test/java/io/agrest/exp/parser/ExpBitwiseRightShiftTest.java
+++ b/agrest-engine/src/test/java/io/agrest/exp/parser/ExpBitwiseRightShiftTest.java
@@ -26,8 +26,8 @@ void parse(String expString) {
 
     @ParameterizedTest
     @CsvSource(delimiter = '|', value = {
-            "1>>2|(1) >> (2)",
-            "1 >>  2|(1) >> (2)"
+            "1>>2|1 >> 2",
+            "1 >>  2|1 >> 2"
     })
     public void parsedToString(String expString, String expected) {
         assertEquals(expected, Exp.parse(expString).toString());
diff --git a/agrest-engine/src/test/java/io/agrest/exp/parser/ExpBitwiseXorTest.java b/agrest-engine/src/test/java/io/agrest/exp/parser/ExpBitwiseXorTest.java
index de3307671..5c98b323e 100644
--- a/agrest-engine/src/test/java/io/agrest/exp/parser/ExpBitwiseXorTest.java
+++ b/agrest-engine/src/test/java/io/agrest/exp/parser/ExpBitwiseXorTest.java
@@ -26,8 +26,8 @@ void parse(String expString) {
 
     @ParameterizedTest
     @CsvSource(delimiter = '|', value = {
-            "1^2|(1) ^ (2)",
-            "1 ^  2|(1) ^ (2)"
+            "1^2|1 ^ 2",
+            "1 ^  2|1 ^ 2"
     })
     public void parsedToString(String expString, String expected) {
         assertEquals(expected, Exp.parse(expString).toString());
diff --git a/agrest-engine/src/test/java/io/agrest/exp/parser/ExpDivideTest.java b/agrest-engine/src/test/java/io/agrest/exp/parser/ExpDivideTest.java
index 2b5719544..a706c90e8 100644
--- a/agrest-engine/src/test/java/io/agrest/exp/parser/ExpDivideTest.java
+++ b/agrest-engine/src/test/java/io/agrest/exp/parser/ExpDivideTest.java
@@ -27,8 +27,8 @@ void parse(String expString) {
 
     @ParameterizedTest
     @CsvSource(delimiter = '|', value = {
-            "1/2|(1) / (2)",
-            "1 /  2|(1) / (2)"
+            "1/2|1 / 2",
+            "1 /  2|1 / 2"
     })
     public void parsedToString(String expString, String expected) {
         assertEquals(expected, Exp.parse(expString).toString());
diff --git a/agrest-engine/src/test/java/io/agrest/exp/parser/ExpEqualTest.java b/agrest-engine/src/test/java/io/agrest/exp/parser/ExpEqualTest.java
index 9969bf0c5..50fdda066 100644
--- a/agrest-engine/src/test/java/io/agrest/exp/parser/ExpEqualTest.java
+++ b/agrest-engine/src/test/java/io/agrest/exp/parser/ExpEqualTest.java
@@ -29,8 +29,8 @@ public void parse(String expString) {
 
     @ParameterizedTest
     @CsvSource(delimiter = '|', value = {
-            "a=b|(a) = (b)",
-            "a = b|(a) = (b)"
+            "a=b|a = b",
+            "a = b|a = b"
     })
     public void parsedToString(String expString, String expected) {
         assertEquals(expected, Exp.parse(expString).toString());
diff --git a/agrest-engine/src/test/java/io/agrest/exp/parser/ExpGreaterOrEqualTest.java b/agrest-engine/src/test/java/io/agrest/exp/parser/ExpGreaterOrEqualTest.java
index a2d3f6f39..3bb7a8471 100644
--- a/agrest-engine/src/test/java/io/agrest/exp/parser/ExpGreaterOrEqualTest.java
+++ b/agrest-engine/src/test/java/io/agrest/exp/parser/ExpGreaterOrEqualTest.java
@@ -30,8 +30,8 @@ void parse(String expString) {
 
     @ParameterizedTest
     @CsvSource(delimiter = '|', value = {
-            "a>=b|(a) >= (b)",
-            "a >= b|(a) >= (b)"
+            "a>=b|a >= b",
+            "a >= b|a >= b"
     })
     public void parsedToString(String expString, String expected) {
         assertEquals(expected, Exp.parse(expString).toString());
diff --git a/agrest-engine/src/test/java/io/agrest/exp/parser/ExpGreaterTest.java b/agrest-engine/src/test/java/io/agrest/exp/parser/ExpGreaterTest.java
index 5cc48e2f4..7a2a5b760 100644
--- a/agrest-engine/src/test/java/io/agrest/exp/parser/ExpGreaterTest.java
+++ b/agrest-engine/src/test/java/io/agrest/exp/parser/ExpGreaterTest.java
@@ -30,8 +30,8 @@ void parse(String expString) {
 
     @ParameterizedTest
     @CsvSource(delimiter = '|', value = {
-            "a>b|(a) > (b)",
-            "a > b|(a) > (b)"
+            "a>b|a > b",
+            "a > b|a > b"
     })
     public void parsedToString(String expString, String expected) {
         assertEquals(expected, Exp.parse(expString).toString());
diff --git a/agrest-engine/src/test/java/io/agrest/exp/parser/ExpLessOrEqualTest.java b/agrest-engine/src/test/java/io/agrest/exp/parser/ExpLessOrEqualTest.java
index c4d164b16..0b69d45f8 100644
--- a/agrest-engine/src/test/java/io/agrest/exp/parser/ExpLessOrEqualTest.java
+++ b/agrest-engine/src/test/java/io/agrest/exp/parser/ExpLessOrEqualTest.java
@@ -29,8 +29,8 @@ void parse(String expString) {
 
     @ParameterizedTest
     @CsvSource(delimiter = '|', value = {
-            "a<=b|(a) <= (b)",
-            "a <= b|(a) <= (b)"
+            "a<=b|a <= b",
+            "a <= b|a <= b"
     })
     public void parsedToString(String expString, String expected) {
         assertEquals(expected, Exp.parse(expString).toString());
diff --git a/agrest-engine/src/test/java/io/agrest/exp/parser/ExpLessTest.java b/agrest-engine/src/test/java/io/agrest/exp/parser/ExpLessTest.java
index 64019c734..64c209d7b 100644
--- a/agrest-engine/src/test/java/io/agrest/exp/parser/ExpLessTest.java
+++ b/agrest-engine/src/test/java/io/agrest/exp/parser/ExpLessTest.java
@@ -32,8 +32,8 @@ void parse(String expString) {
 
     @ParameterizedTest
     @CsvSource(delimiter = '|', value = {
-            "a<b|(a) < (b)",
-            "a < b|(a) < (b)"
+            "a<b|a < b",
+            "a < b|a < b"
     })
     public void parsedToString(String expString, String expected) {
         assertEquals(expected, Exp.parse(expString).toString());
diff --git a/agrest-engine/src/test/java/io/agrest/exp/parser/ExpMultiplyTest.java b/agrest-engine/src/test/java/io/agrest/exp/parser/ExpMultiplyTest.java
index 3affa8d7a..5cca6fbbe 100644
--- a/agrest-engine/src/test/java/io/agrest/exp/parser/ExpMultiplyTest.java
+++ b/agrest-engine/src/test/java/io/agrest/exp/parser/ExpMultiplyTest.java
@@ -27,8 +27,8 @@ void parse(String expString) {
 
     @ParameterizedTest
     @CsvSource(delimiter = '|', value = {
-            "1*2|(1) * (2)",
-            "1 *  2|(1) * (2)"
+            "1*2|1 * 2",
+            "1 *  2|1 * 2"
     })
     public void parsedToString(String expString, String expected) {
         assertEquals(expected, Exp.parse(expString).toString());
diff --git a/agrest-engine/src/test/java/io/agrest/exp/parser/ExpNegateTest.java b/agrest-engine/src/test/java/io/agrest/exp/parser/ExpNegateTest.java
index 25e2b8e56..d748987a5 100644
--- a/agrest-engine/src/test/java/io/agrest/exp/parser/ExpNegateTest.java
+++ b/agrest-engine/src/test/java/io/agrest/exp/parser/ExpNegateTest.java
@@ -26,8 +26,8 @@ void parse(String expString) {
 
     @ParameterizedTest
     @CsvSource(delimiter = '|', value = {
-            "-a|-(a)",
-            "- a|-(a)"
+            "-a|-a",
+            "- a|-a"
     })
     public void parsedToString(String expString, String expected) {
         assertEquals(expected, Exp.parse(expString).toString());
diff --git a/agrest-engine/src/test/java/io/agrest/exp/parser/ExpNotEqualTest.java b/agrest-engine/src/test/java/io/agrest/exp/parser/ExpNotEqualTest.java
index a8d810896..58a754b54 100644
--- a/agrest-engine/src/test/java/io/agrest/exp/parser/ExpNotEqualTest.java
+++ b/agrest-engine/src/test/java/io/agrest/exp/parser/ExpNotEqualTest.java
@@ -29,9 +29,9 @@ public void parse(String expString) {
 
     @ParameterizedTest
     @CsvSource(delimiter = '|', value = {
-            "a!=b|(a) != (b)",
-            "a <> b|(a) != (b)",
-            "a !=  b|(a) != (b)"
+            "a!=b|a != b",
+            "a <> b|a != b",
+            "a !=  b|a != b"
     })
     public void parsedToString(String expString, String expected) {
         assertEquals(expected, Exp.parse(expString).toString());
diff --git a/agrest-engine/src/test/java/io/agrest/exp/parser/ExpNotTest.java b/agrest-engine/src/test/java/io/agrest/exp/parser/ExpNotTest.java
index d156af9da..1d2ed2a60 100644
--- a/agrest-engine/src/test/java/io/agrest/exp/parser/ExpNotTest.java
+++ b/agrest-engine/src/test/java/io/agrest/exp/parser/ExpNotTest.java
@@ -24,10 +24,10 @@ void parse(String expString) {
 
     @ParameterizedTest
     @CsvSource(delimiter = '|', value = {
-            "!a|not (a)",
-            "! a|not (a)",
-            "not a|not (a)",
-            "not (a)|not (a)"
+            "!a|not a",
+            "! a|not a",
+            "not a|not a",
+            "not (a)|not a"
     })
     public void parsedToString(String expString, String expected) {
         assertEquals(expected, Exp.parse(expString).toString());
diff --git a/agrest-engine/src/test/java/io/agrest/exp/parser/ExpSubtractTest.java b/agrest-engine/src/test/java/io/agrest/exp/parser/ExpSubtractTest.java
index 404049539..ca0d617da 100644
--- a/agrest-engine/src/test/java/io/agrest/exp/parser/ExpSubtractTest.java
+++ b/agrest-engine/src/test/java/io/agrest/exp/parser/ExpSubtractTest.java
@@ -26,8 +26,8 @@ void parse(String expString) {
 
     @ParameterizedTest
     @CsvSource(delimiter = '|', value = {
-            "1-2|(1) - (2)",
-            "1 -  2|(1) - (2)"
+            "1-2|1 - 2",
+            "1 -  2|1 - 2"
     })
     public void parsedToString(String expString, String expected) {
         assertEquals(expected, Exp.parse(expString).toString());
diff --git a/agrest-engine/src/test/java/io/agrest/protocol/ExpTest.java b/agrest-engine/src/test/java/io/agrest/protocol/ExpTest.java
index 141dd96c3..55db08c68 100644
--- a/agrest-engine/src/test/java/io/agrest/protocol/ExpTest.java
+++ b/agrest-engine/src/test/java/io/agrest/protocol/ExpTest.java
@@ -26,7 +26,7 @@ public void namedParams() {
         params.put("d", 16);
 
         assertEquals(
-                "(((a) = (2)) and ((b) = (4))) or (((c) = (null)) and (not ((d) = (16))))",
+                "((a = 2) and (b = 4)) or ((c = null) and (not (d = 16)))",
                 exp.namedParams(params).toString());
     }
 
@@ -35,15 +35,15 @@ public void namedParams_Pruning() {
         Exp exp = Exp.parse("a = $a and b = $b or c = $c and not d = $d");
 
         Map<String, Object> params1 = Map.of("a", 2, "b", 4, "c", 8);
-        assertEquals("(((a) = (2)) and ((b) = (4))) or ((c) = (8))", exp.namedParams(params1).toString());
+        assertEquals("((a = 2) and (b = 4)) or (c = 8)", exp.namedParams(params1).toString());
 
         Map<String, Object> params2 = Map.of("c", 8);
-        assertEquals("(c) = (8)", exp.namedParams(params2).toString());
+        assertEquals("c = 8", exp.namedParams(params2).toString());
 
         Map<String, Object> params3 = new HashMap<>();
         params3.put("a", null);
         params3.put("c", 8);
-        assertEquals("((a) = (null)) or ((c) = (8))", exp.namedParams(params3).toString());
+        assertEquals("(a = null) or (c = 8)", exp.namedParams(params3).toString());
     }
 
     @Test
@@ -51,13 +51,13 @@ public void namedParams_NoPruning() {
         Exp exp = Exp.parse("a = $a and b = $b or c = $c and not d = $d");
 
         Map<String, Object> params1 = Map.of("a", 2, "b", 4, "c", 8);
-        assertEquals("(((a) = (2)) and ((b) = (4))) or (((c) = (8)) and (not ((d) = ($d))))",
+        assertEquals("((a = 2) and (b = 4)) or ((c = 8) and (not (d = $d)))",
                 exp.namedParams(params1, false).toString());
 
         Map<String, Object> params2 = new HashMap<>();
         params2.put("a", null);
         params2.put("c", 8);
-        assertEquals("(((a) = (null)) and ((b) = ($b))) or (((c) = (8)) and (not ((d) = ($d))))",
+        assertEquals("((a = null) and (b = $b)) or ((c = 8) and (not (d = $d)))",
                 exp.namedParams(params2, false).toString());
     }
 
@@ -85,9 +85,9 @@ public void paramsImmutable() {
         Exp e1 = raw.positionalParams("b");
         Exp e2 = raw.namedParams(Map.of("1", "c"));
 
-        assertEquals("(a) = ($1)", raw.toString());
-        assertEquals("(a) = ('b')", e1.toString());
-        assertEquals("(a) = ('c')", e2.toString());
+        assertEquals("a = $1", raw.toString());
+        assertEquals("a = 'b'", e1.toString());
+        assertEquals("a = 'c'", e2.toString());
     }
 
     @Test
@@ -102,11 +102,11 @@ public void andOrImmutable() {
         assertEquals(5, new ArrayList<>(new HashSet<>(all)).size(), "Some expressions were reused");
 
 
-        assertEquals("(1) > (2)", e1.toString());
-        assertEquals("((1) > (2)) and ((3) < (4))", e2.toString());
-        assertEquals("((1) > (2)) or ((5) = (6))", e3.toString());
-        assertEquals("(((1) > (2)) and ((3) < (4))) or ((7) > (8))", e4.toString());
-        assertEquals("(((1) > (2)) or ((5) = (6))) and ((9) < (10))", e5.toString());
+        assertEquals("1 > 2", e1.toString());
+        assertEquals("(1 > 2) and (3 < 4)", e2.toString());
+        assertEquals("(1 > 2) or (5 = 6)", e3.toString());
+        assertEquals("((1 > 2) and (3 < 4)) or (7 > 8)", e4.toString());
+        assertEquals("((1 > 2) or (5 = 6)) and (9 < 10)", e5.toString());
     }
 
     @Test
@@ -118,10 +118,10 @@ public void positionalParamsThrowsOnTooFewParams() {
     public void namedParams_PartialResolution() {
 
         Exp p1 = Exp.parse("a = $a").namedParams(Collections.emptyMap(), false);
-        assertEquals("(a) = ($a)", p1.toString());
+        assertEquals("a = $a", p1.toString());
 
         Exp p2 = Exp.parse("a = $a and b = $b").namedParams(Map.of("b", 1), false);
-        assertEquals("((a) = ($a)) and ((b) = (1))", p2.toString());
+        assertEquals("(a = $a) and (b = 1)", p2.toString());
     }
 
     @Test
@@ -146,17 +146,17 @@ public void notBetween() {
 
     @Test
     public void equal() {
-        assertEquals("(a) = ('b')", Exp.equal("a", "b").toString());
+        assertEquals("a = 'b'", Exp.equal("a", "b").toString());
     }
 
     @Test
     public void notEqual() {
-        assertEquals("(a) != ('b')", Exp.notEqual("a", "b").toString());
+        assertEquals("a != 'b'", Exp.notEqual("a", "b").toString());
     }
 
     @Test
     public void lessOrEqual() {
-        assertEquals("(a) <= (5)", Exp.lessOrEqual("a", 5).toString());
+        assertEquals("a <= 5", Exp.lessOrEqual("a", 5).toString());
     }
 
     @Test
@@ -201,7 +201,7 @@ public void notInCollection() {
 
     @Test
     public void not() {
-        assertEquals("not ((a) = (5))", Exp.not(Exp.equal("a", 5)).toString());
-        assertEquals("(a) = (5)", Exp.not(Exp.not(Exp.equal("a", 5))).toString());
+        assertEquals("not (a = 5)", Exp.not(Exp.equal("a", 5)).toString());
+        assertEquals("a = 5", Exp.not(Exp.not(Exp.equal("a", 5))).toString());
     }
 }
diff --git a/agrest-engine/src/test/java/io/agrest/runtime/protocol/ExpParserTest.java b/agrest-engine/src/test/java/io/agrest/runtime/protocol/ExpParserTest.java
index fd12ee2fa..14c527d7e 100644
--- a/agrest-engine/src/test/java/io/agrest/runtime/protocol/ExpParserTest.java
+++ b/agrest-engine/src/test/java/io/agrest/runtime/protocol/ExpParserTest.java
@@ -21,55 +21,55 @@ public static void beforeAll() {
     public void fromString_Bare() {
         Exp exp = parser.fromString("a = 12345 and b = 'John Smith' and c = true");
         assertNotNull(exp);
-        assertEquals("((a) = (12345)) and ((b) = ('John Smith')) and ((c) = (true))", exp.toString());
+        assertEquals("(a = 12345) and (b = 'John Smith') and (c = true)", exp.toString());
     }
 
     @Test
     public void fromString_Functions_Paths() {
         Exp exp = parser.fromString("length(b) > 5");
         assertNotNull(exp);
-        assertEquals("(length(b)) > (5)", exp.toString());
+        assertEquals("length(b) > 5", exp.toString());
     }
 
     @Test
     public void fromString_List() {
         Exp exp = parser.fromString("[\"a = 12345 and b = 'John Smith' and c = true\"]");
         assertNotNull(exp);
-        assertEquals("((a) = (12345)) and ((b) = ('John Smith')) and ((c) = (true))", exp.toString());
+        assertEquals("(a = 12345) and (b = 'John Smith') and (c = true)", exp.toString());
     }
 
     @Test
     public void fromString_List_Params_String() {
         Exp exp = parser.fromString("[\"b=$s\",\"x\"]");
         assertNotNull(exp);
-        assertEquals("(b) = ('x')", exp.toString());
+        assertEquals("b = 'x'", exp.toString());
     }
 
     @Test
     public void fromString_List_Params_Multiple() {
         Exp exp = parser.fromString("[\"b=$s or b =$x or b =$s\",\"x\",\"y\"]");
         assertNotNull(exp);
-        assertEquals("((b) = ('x')) or ((b) = ('y')) or ((b) = ('x'))", exp.toString());
+        assertEquals("(b = 'x') or (b = 'y') or (b = 'x')", exp.toString());
     }
 
     @Test
     public void fromString_Map() {
         Exp exp = parser.fromString("{\"exp\" : \"a = 12345 and b = 'John Smith' and c = true\"}");
         assertNotNull(exp);
-        assertEquals("((a) = (12345)) and ((b) = ('John Smith')) and ((c) = (true))", exp.toString());
+        assertEquals("(a = 12345) and (b = 'John Smith') and (c = true)", exp.toString());
     }
 
     @Test
     public void fromString_Map_Params_String() {
         Exp exp = parser.fromString("{\"exp\" : \"b=$s\", \"params\":{\"s\":\"x\"}}");
         assertNotNull(exp);
-        assertEquals("(b) = ('x')", exp.toString());
+        assertEquals("b = 'x'", exp.toString());
     }
 
     @Test
     public void fromString_Map_Params_Null() {
         Exp exp = parser.fromString("{\"exp\" : \"c=$b\", \"params\":{\"b\": null}}");
         assertNotNull(exp);
-        assertEquals("(c) = (null)", exp.toString());
+        assertEquals("c = null", exp.toString());
     }
 }