diff --git a/predicators/structs.py b/predicators/structs.py
index 8f113ce2af..f5363e9f3b 100644
--- a/predicators/structs.py
+++ b/predicators/structs.py
@@ -315,6 +315,7 @@ def _negated_classifier(self, state: State,
         return not self._classifier(state, objects)
 
 
+@dataclass(frozen=True, order=True, repr=False)
 class VLMPredicate(Predicate):
     """Struct defining a predicate (a lifted classifier over states) that uses
     a VLM for evaluation.
@@ -325,7 +326,10 @@ class VLMPredicate(Predicate):
     at once.
     """
 
+    # A classifier is not needed for VLM predicates
     _classifier: Optional[Callable[[State, Sequence[Object]], bool]] = None
+    # An optional prompt additionally provided for each VLM predicate
+    prompt: Optional[str] = None
 
     def holds(self, state: State, objects: Sequence[Object]) -> bool:
         """Public method for getting predicate value.
@@ -463,7 +467,6 @@ class VLMGroundAtom(GroundAtom):
 
     # NOTE: This subclasses GroundAtom to support VLM predicates and classifiers
     predicate: VLMPredicate
-    prompt: Optional[str] = None
 
     def get_query_str(self, without_type: bool = False) -> str:
         """Get a query string for this ground atom.
@@ -478,8 +481,8 @@ def get_query_str(self, without_type: bool = False) -> str:
         else:
             string = str(self)
 
-        if self.prompt is not None:
-            string += f" [Prompt: {self.prompt}]"
+        if self.predicate.prompt is not None:
+            string += f" [Prompt: {self.predicate.prompt}]"
         return string
 
     def holds(self, state: State) -> bool: