diff --git a/core/config/config.go b/core/config/config.go
index 8fc6aaa33..a9cccf036 100644
--- a/core/config/config.go
+++ b/core/config/config.go
@@ -22,6 +22,7 @@ func ResetGlobalConfig(config *Entity) {
 	globalCfg = config
 }
 
+// InitConfigWithYaml loads general configuration from the YAML file under provided path.
 func InitConfigWithYaml(filePath string) (err error) {
 	// Initialize general config and logging module.
 	if err = applyYamlConfigFile(filePath); err != nil {
diff --git a/core/config/doc.go b/core/config/doc.go
new file mode 100644
index 000000000..e8b671e61
--- /dev/null
+++ b/core/config/doc.go
@@ -0,0 +1,2 @@
+// Package config provides general configuration mechanism.
+package config
diff --git a/core/hotspot/doc.go b/core/hotspot/doc.go
new file mode 100644
index 000000000..b5da1dfeb
--- /dev/null
+++ b/core/hotspot/doc.go
@@ -0,0 +1,2 @@
+// Package hotspot provides implementation of "hot-spot" (frequent) parameter flow control.
+package hotspot
diff --git a/core/isolation/doc.go b/core/isolation/doc.go
index bb706260a..d4ef5836b 100644
--- a/core/isolation/doc.go
+++ b/core/isolation/doc.go
@@ -1,3 +1,2 @@
-// Package isolation implements the concurrency traffic control.
-
+// Package isolation provides implementation of concurrency limiting (semaphore isolation).
 package isolation
diff --git a/core/isolation/slot.go b/core/isolation/slot.go
index d02940e79..0f4e7d6e6 100644
--- a/core/isolation/slot.go
+++ b/core/isolation/slot.go
@@ -33,7 +33,7 @@ func (s *Slot) Check(ctx *base.EntryContext) *base.TokenResult {
 		return result
 	}
 	if passed, rule, snapshot := checkPass(ctx); !passed {
-		msg := "isolation check blocked"
+		msg := "concurrency exceeds threshold"
 		if result == nil {
 			result = base.NewTokenResultBlockedWithCause(base.BlockTypeIsolation, msg, rule, snapshot)
 		} else {
diff --git a/core/stat/base/doc.go b/core/stat/base/doc.go
new file mode 100644
index 000000000..a6dc7a88d
--- /dev/null
+++ b/core/stat/base/doc.go
@@ -0,0 +1,2 @@
+// Package stat/base provides fundamental data structures of statistics.
+package base
diff --git a/core/system/doc.go b/core/system/doc.go
new file mode 100644
index 000000000..a49b881b8
--- /dev/null
+++ b/core/system/doc.go
@@ -0,0 +1,2 @@
+// Package system provides implementation of adaptive system protection.
+package system
diff --git a/ext/datasource/doc.go b/ext/datasource/doc.go
new file mode 100644
index 000000000..6bebeaef2
--- /dev/null
+++ b/ext/datasource/doc.go
@@ -0,0 +1,2 @@
+// Package ext/datasource provides interfaces and helper classes of dynamic data-source.
+package datasource