diff --git a/common/type.go b/common/type.go
index 272c0cefd..9cb073744 100644
--- a/common/type.go
+++ b/common/type.go
@@ -6,13 +6,15 @@ import (
 	"reflect"
 )
 
-type creator func(ctx context.Context, config interface{}) (interface{}, error)
+// ConfigCreator is a function to create an object by a config.
+type ConfigCreator func(ctx context.Context, config interface{}) (interface{}, error)
 
 var (
-	typeCreatorRegistry = make(map[reflect.Type]creator)
+	typeCreatorRegistry = make(map[reflect.Type]ConfigCreator)
 )
 
-func RegisterConfig(config interface{}, configCreator creator) error {
+// RegisterConfig registers a global config creator. The config can be nil but must have a type.
+func RegisterConfig(config interface{}, configCreator ConfigCreator) error {
 	configType := reflect.TypeOf(config)
 	if _, found := typeCreatorRegistry[configType]; found {
 		return errors.New("Common: " + configType.Name() + " is already registered.")
@@ -21,6 +23,7 @@ func RegisterConfig(config interface{}, configCreator creator) error {
 	return nil
 }
 
+// CreateObject creates an object by its config. The config type must be registered through RegisterConfig().
 func CreateObject(ctx context.Context, config interface{}) (interface{}, error) {
 	configType := reflect.TypeOf(config)
 	creator, found := typeCreatorRegistry[configType]
diff --git a/proxy/proxy.go b/proxy/proxy.go
index 67b7c3c86..26283f1f6 100644
--- a/proxy/proxy.go
+++ b/proxy/proxy.go
@@ -1,4 +1,8 @@
 // Package proxy contains all proxies used by V2Ray.
+//
+// To implement an inbound or outbound proxy, one needs to do the following:
+// 1. Implement the interface(s) below.
+// 2. Register a config creator through common.RegisterConfig.
 package proxy
 
 import (