diff --git a/core.go b/core.go
new file mode 100644
index 000000000..9ad48eaed
--- /dev/null
+++ b/core.go
@@ -0,0 +1,2 @@
+// Package core provides common definitions and functionalities of V2Ray.
+package core
diff --git a/io/vmessreader.go b/io/vmessreader.go
index 74ab0c2fa..5a7744c17 100644
--- a/io/vmessreader.go
+++ b/io/vmessreader.go
@@ -4,6 +4,7 @@ import (
 	"net"
 )
 
+// VMessInput implements the input message of VMess protocol.
 type VMessInput struct {
 	version  byte
 	userHash [16]byte
diff --git a/vconfig.go b/vconfig.go
index 29ff3b284..6d3bac66f 100644
--- a/vconfig.go
+++ b/vconfig.go
@@ -1,14 +1,27 @@
 package core
 
+// User account that is used for connection to a VPoint
 type VUser struct {
+	// The ID of this VUser. This ID is served as an access token.
+	// It is not necessary to be permanent.
 	id VID
 }
 
+// The next VPoint server in the connection chain.
+type VNext struct {
+	// Address of VNext server, in the form of "IP:Port"
+	ServerAddress string
+	// User accounts for accessing VNext.
+	User []VUser
+}
+
+// The config for VPoint server.
 type VConfig struct {
-	RunAs           VUser
-	Port            uint16
-	AllowedClients  []VUser
-	AllowedProtocol string
+	// Port of this VPoint server.
+	Port           uint16
+	AllowedClients []VUser
+	ClientProtocol string
+	VNextList      []VNext
 }
 
 type VConfigMarshaller interface {
diff --git a/vid.go b/vid.go
index d82b422af..29ca2042d 100644
--- a/vid.go
+++ b/vid.go
@@ -5,6 +5,7 @@ import (
 	"fmt"
 )
 
+// The ID of en entity, in the form of an UUID.
 type VID [16]byte
 
 var byteGroups = []int{8, 4, 4, 4, 12}
diff --git a/vpoint.go b/vpoint.go
index b0b0f94d7..b0c97c02c 100644
--- a/vpoint.go
+++ b/vpoint.go
@@ -9,8 +9,11 @@ type VPoint struct {
 	connHandler ConnectionHandler
 }
 
+// NewVPoint returns a new VPoint server based on given configuration.
+// The server is not started at this point.
 func NewVPoint(config *VConfig) (*VPoint, error) {
-	var vpoint *VPoint
+	var vpoint = new(VPoint)
+	vpoint.config = *config
 	return vpoint, nil
 }
 
@@ -18,6 +21,8 @@ type ConnectionHandler interface {
 	Listen(port uint16) error
 }
 
+// Start starts the VPoint server, and return any error during the process.
+// In the case of any errors, the state of the server is unpredicatable.
 func (vp *VPoint) Start() error {
 	if vp.config.Port <= 0 {
 		return fmt.Errorf("Invalid port %d", vp.config.Port)