diff --git a/command.go b/command.go
index ea1bd927..3dd475fa 100644
--- a/command.go
+++ b/command.go
@@ -18,10 +18,22 @@ import (
 )
 
 type Cmder interface {
+	// command name.
+	// e.g. "set k v ex 10" -> "set", "cluster info" -> "cluster".
 	Name() string
+
+	// full command name.
+	// e.g. "set k v ex 10" -> "set", "cluster info" -> "cluster info".
 	FullName() string
+
+	// all args of the command.
+	// e.g. "set k v ex 10" -> "[set k v ex 10]".
 	Args() []interface{}
+
+	// format request and response string.
+	// e.g. "set k v ex 10" -> "set k v ex 10: OK", "get k" -> "get k: v".
 	String() string
+
 	stringArg(int) string
 	firstKeyPos() int8
 	SetFirstKeyPos(int8)