diff --git a/lua/core/engine.lua b/lua/core/engine.lua
index 660742dd..eb88a399 100644
--- a/lua/core/engine.lua
+++ b/lua/core/engine.lua
@@ -1,3 +1,11 @@
+---@class Engine : Object
+---@field packages table
+---@field skills table
+---@field related_skills table
+---@field generals table
+---@field lords table
+---@field cards table
+---@field translations table
 local Engine = class("Engine")
 
 function Engine:initialize()
@@ -20,7 +28,7 @@ function Engine:initialize()
     self:loadPackages()
 end
 
--- Package pack
+---@param pack Package
 function Engine:loadPackage(pack)
     assert(pack:isInstanceOf(Package))
     if self.packages[pack.name] ~= nil then 
@@ -48,6 +56,7 @@ function Engine:loadPackages()
     FileIO.cd("..")
 end
 
+---@param t table
 function Engine:loadTranslationTable(t)
     assert(type(t) == "table")
     for k, v in pairs(t) do
@@ -55,6 +64,7 @@ function Engine:loadTranslationTable(t)
     end
 end
 
+---@param skill any
 function Engine:addSkill(skill)
     assert(skill.class:isSubclassOf(Skill))
     if self.skills[skill.name] ~= nil then
@@ -63,6 +73,7 @@ function Engine:addSkill(skill)
     self.skills[skill.name] = skill
 end
 
+---@param skills any[]
 function Engine:addSkills(skills)
     assert(type(skills) == "table")
     for _, skill in ipairs(skills) do
@@ -70,6 +81,7 @@ function Engine:addSkills(skills)
     end
 end
 
+---@param general General
 function Engine:addGeneral(general)
     assert(general:isInstanceOf(General))
     if self.generals[general.name] ~= nil then
@@ -78,6 +90,7 @@ function Engine:addGeneral(general)
     self.generals[general.name] = general
 end
 
+---@param generals General[]
 function Engine:addGenerals(generals)
     assert(type(generals) == "table")
     for _, general in ipairs(generals) do
@@ -97,6 +110,11 @@ function Engine:addCards(cards)
     end
 end
 
+---@param num number
+---@param generalPool General[]
+---@param except string[]
+---@param filter function
+---@return General[] generals
 function Engine:getGeneralsRandomly(num, generalPool, except, filter)
     if filter then
         assert(type(filter) == "function")
@@ -130,6 +148,8 @@ function Engine:getGeneralsRandomly(num, generalPool, except, filter)
     return result
 end
 
+---@param except General[]
+---@return General[]
 function Engine:getAllGenerals(except)
     local result = {}
     for _, general in ipairs(self.generals) do
diff --git a/lua/core/general.lua b/lua/core/general.lua
index 496de06f..4c3f68b7 100644
--- a/lua/core/general.lua
+++ b/lua/core/general.lua
@@ -1,3 +1,4 @@
+--- @class General : Object
 General = class("General")
 
 -- enum Gender
@@ -18,6 +19,7 @@ function General:initialize(package, name, kingdom, hp, maxHp, gender, initialHp
     self.other_skills = {}  -- string[]
 end
 
+---@param skill any
 function General:addSkill(skill)
     if (type(skill) == "string") then
         table.insert(self.other_skills, skill)
diff --git a/lua/core/package.lua b/lua/core/package.lua
index 0d713634..aa1c5700 100644
--- a/lua/core/package.lua
+++ b/lua/core/package.lua
@@ -1,3 +1,10 @@
+---@class Package : Object
+---@field name string
+---@field type number
+---@field generals table
+---@field extra_skills table
+---@field related_skills table
+---@field cards table
 local Package = class("Package")
 
 -- enum Type
@@ -5,7 +12,6 @@ Package.GeneralPack = 0
 Package.CardPack = 1
 Package.SpecialPack = 2
 
--- string name, Type type
 function Package:initialize(name, _type)
     assert(type(name) == "string")
     assert(type(_type) == "nil" or type(_type) == "number")
@@ -20,6 +26,7 @@ function Package:initialize(name, _type)
     self.cards = {}     --> Card[]
 end
 
+---@return table skills
 function Package:getSkills()
     local ret = {table.unpack(self.related_skills)}
     if self.type == Package.GeneralPack then
@@ -32,6 +39,7 @@ function Package:getSkills()
     return ret
 end
 
+---@param general General
 function Package:addGeneral(general)
     assert(general.class and general:isInstanceOf(General))
     table.insert(self.generals, general)
diff --git a/lua/core/player.lua b/lua/core/player.lua
index 92c591af..d6c188fb 100644
--- a/lua/core/player.lua
+++ b/lua/core/player.lua
@@ -1,3 +1,4 @@
+---@class Player : Object
 local Player = class("Player")
 
 function Player:initialize()
diff --git a/lua/core/util.lua b/lua/core/util.lua
index 73ed643a..fa9e27d3 100644
--- a/lua/core/util.lua
+++ b/lua/core/util.lua
@@ -29,16 +29,29 @@ function table:insertTable(list)
 	end
 end
 
+---@class Sql
 Sql = {
+	---@param filename string
 	open = function(filename)
 		return freekill.OpenDatabase(filename)
 	end,
+
+	---@param db freekill.SQLite3
 	close = function(db)
 		freekill.CloseDatabase(db)
 	end,
+
+	--- Execute an SQL statement.
+	---@param db freekill.SQLite3
+	---@param sql string
 	exec = function(db, sql)
 		freekill.ExecSQL(db, sql)
 	end,
+
+	--- Execute a `SELECT` SQL statement.
+	---@param db freekill.SQLite3
+	---@param sql string
+	---@return table data # { [columnName] --> result : string[] }
 	exec_select = function(db, sql)
 		return json.decode(freekill.SelectFromDb(db, sql))
 	end,
diff --git a/lua/freekill.lua b/lua/freekill.lua
index 3899c84e..faa7a3f9 100644
--- a/lua/freekill.lua
+++ b/lua/freekill.lua
@@ -5,8 +5,13 @@ package.path = package.path .. ";./lua/lib/?.lua"
                             .. ";./lua/?.lua"
 
 -- load libraries
+
+---@type class
 class = require "middleclass"
+
+---@type json
 json = require "json"
+
 require "sha256"
 Util = require "core.util"
 math.randomseed(os.time())
diff --git a/lua/server/gamelogic.lua b/lua/server/gamelogic.lua
index 6f569a6e..551e6af2 100644
--- a/lua/server/gamelogic.lua
+++ b/lua/server/gamelogic.lua
@@ -1,3 +1,4 @@
+---@class GameLogic: Object
 local GameLogic = class("GameLogic")
 
 function GameLogic:initialize(room)
diff --git a/lua/server/room.lua b/lua/server/room.lua
index 6e6f00e9..00718af8 100644
--- a/lua/server/room.lua
+++ b/lua/server/room.lua
@@ -1,3 +1,4 @@
+---@class Room : Object
 local Room = class("Room")
 
 function Room:initialize(_room)
@@ -13,6 +14,7 @@ function Room:run()
     for _, p in freekill.qlist(self.room:getPlayers()) do
         local player = ServerPlayer:new(p)
         player.state = p:getStateString()
+        player.room = self
         table.insert(self.players, player)
         self.server.players[player:getId()] = player
     end
diff --git a/lua/server/server.lua b/lua/server/server.lua
index 3c5abbce..6c953b7d 100644
--- a/lua/server/server.lua
+++ b/lua/server/server.lua
@@ -1,3 +1,4 @@
+---@class Server : Object
 Server = class('Server')
 
 -- load server classes
diff --git a/lua/server/serverplayer.lua b/lua/server/serverplayer.lua
index 4590f79c..3bf61cad 100644
--- a/lua/server/serverplayer.lua
+++ b/lua/server/serverplayer.lua
@@ -1,8 +1,10 @@
+---@class ServerPlayer : Player
 local ServerPlayer = Player:subclass("ServerPlayer")
 
 function ServerPlayer:initialize(_self)
     Player.initialize(self)
     self.serverplayer = _self
+    self.room = nil
 
     self.next = nil
 
diff --git a/lua/vscode/freekill.lua b/lua/vscode/freekill.lua
new file mode 100644
index 00000000..b2dd0aa2
--- /dev/null
+++ b/lua/vscode/freekill.lua
@@ -0,0 +1,25 @@
+---@meta
+
+-- Note: these files are not used by FreeKill.
+-- Just for convenience when using sumneko.lua
+
+---@class freekill
+---FreeKill's lua API
+freekill = {}
+
+---@class freekill.SPlayerList
+SPlayerList = {}
+
+--- * get microsecond from Epoch
+---@return number microsecond
+function freekill:GetMicroSecond()end
+
+--- construct a QList<ServerPlayer *>.
+---@return freekill.SPlayerList
+function freekill:SPlayerList()end
+
+function freekill.QmlBackend_pwd()end
+function freekill.QmlBackend_ls(filename)end
+function freekill.QmlBackend_cd(dir)end
+function freekill.QmlBackend_exists(file)end
+function freekill.QmlBackend_isDir(file)end
diff --git a/lua/vscode/lib.lua b/lua/vscode/lib.lua
new file mode 100644
index 00000000..78d0549b
--- /dev/null
+++ b/lua/vscode/lib.lua
@@ -0,0 +1,33 @@
+---@meta
+
+---@class class
+---@field static any
+--- middleclass
+class = {}
+
+---@class Object
+---@field class class
+Object = {}
+
+function Object:initialize(...) end
+
+function Object.new(...)end
+
+---@param name string
+function Object:subclass(name)end
+
+---@param class class
+---@return boolean
+function Object:isInstanceOf(class) end
+
+---@class json
+json = {}
+
+--- convert obj to JSON string
+---@return string json
+function json.encode(obj)end
+
+--- convert JSON string to lua types
+---@param str string # JSON string to decode
+---@return table|number|string
+function json.decode(str)end
diff --git a/lua/vscode/player.lua b/lua/vscode/player.lua
new file mode 100644
index 00000000..fd99c6d0
--- /dev/null
+++ b/lua/vscode/player.lua
@@ -0,0 +1,64 @@
+---@meta
+
+---@class freekill.Player
+FPlayer = {}
+
+---@return number id
+function FPlayer:getId()end
+
+---@param id number
+function FPlayer:setId(id)end
+
+---@return string name
+function FPlayer:getScreenName()end
+
+---@param name string
+function FPlayer:setScreenName(name)end
+
+---@return string avatar
+function FPlayer:getAvatar()end
+
+---@param avatar string
+function FPlayer:setAvatar(avatar)end
+
+---@return string state
+function FPlayer:getStateString()end
+
+---@param state string
+function FPlayer:setStateString(state)end
+
+---@class freekill.ServerPlayer : freekill.Player
+FServerPlayer = {}
+
+---@return freekill.Server
+function FServerPlayer:getServer()end
+
+---@return freekill.Room
+function FServerPlayer:getRoom()end
+
+---@param room freekill.Room
+function FServerPlayer:setRoom(room)end
+
+---@param msg string
+function FServerPlayer:speak(msg)end
+
+--- Send a request to client, and allow client to reply within *timeout* seconds.
+---
+--- *timeout* must not be negative or **nil**.
+---@param command string
+---@param jsonData string
+---@param timeout number
+function FServerPlayer:doRequest(command,jsonData,timeout)end
+
+--- Wait for at most *timeout* seconds for reply from client.
+---
+--- If *timeout* is negative or **nil**, the function will wait forever until get reply.
+---@param timeout number # seconds to wait
+---@return string reply # JSON data
+---@overload fun()
+function FServerPlayer:waitForReply(timeout)end
+
+--- Notice the client.
+---@param command string
+---@param jsonData string
+function FServerPlayer:doNotify(command,jsonData)end
diff --git a/lua/vscode/qt.lua b/lua/vscode/qt.lua
new file mode 100644
index 00000000..3cc3b3ef
--- /dev/null
+++ b/lua/vscode/qt.lua
@@ -0,0 +1,22 @@
+---@meta
+
+---@return number length
+function SPlayerList:length()end
+
+---@param e freekill.ServerPlayer
+function SPlayerList:append(e)end
+
+---@param e freekill.ServerPlayer
+---@return boolean
+function SPlayerList:contains(e)end
+
+---@param index number
+---@return freekill.ServerPlayer | nil
+function SPlayerList:at(index)end
+
+function SPlayerList:first()end
+function SPlayerList:last()end
+function SPlayerList:isEmpty()end
+function SPlayerList:removeAt(index)end
+function SPlayerList:removeAll()end
+function SPlayerList:indexOf(e)end
diff --git a/lua/vscode/server.lua b/lua/vscode/server.lua
new file mode 100644
index 00000000..be029926
--- /dev/null
+++ b/lua/vscode/server.lua
@@ -0,0 +1,47 @@
+---@meta
+
+---@class freekill.Server
+FServer = {}
+
+---@type freekill.Server
+freekill.ServerInstance = {}
+
+---@class freekill.Room
+--- Room (C++)
+FRoom = {}
+
+---@param owner freekill.ServerPlayer
+---@param name string
+---@param capacity number
+function FServer:createRoom(owner,name,capacity)end
+
+---@param id number
+---@return freekill.Room room
+function FServer:findRoom(id)end
+
+---@param id number
+---@return freekill.ServerPlayer player
+function FServer:findPlayer(id)end
+
+---@return freekill.SQLite3 db
+function FServer:getDatabase()end
+
+function FRoom:getServer()end
+function FRoom:getId()end
+function FRoom:isLobby()end
+function FRoom:getName()end
+function FRoom:setName(name)end
+function FRoom:getCapacity()end
+function FRoom:setCapacity(capacity)end
+function FRoom:isFull()end
+function FRoom:isAbandoned()end
+function FRoom:addPlayer(player)end
+function FRoom:removePlayer(player)end
+function FRoom:getOwner()end
+function FRoom:setOwner(owner)end
+function FRoom:getPlayers()end
+function FRoom:findPlayer(id)end
+function FRoom:getTimeout()end
+function FRoom:isStarted()end
+function FRoom:doBroadcastNotify(targets,command,jsonData)end
+function FRoom:gameOver()end
diff --git a/lua/vscode/sqlite.lua b/lua/vscode/sqlite.lua
new file mode 100644
index 00000000..a53edab7
--- /dev/null
+++ b/lua/vscode/sqlite.lua
@@ -0,0 +1,20 @@
+---@meta
+
+---@class freekill.SQLite3
+SQLite3 = {}
+
+---@param filename string
+---@return freekill.SQLite3
+function freekill.OpenDatabase(filename)end
+
+---@param db freekill.SQLite3
+---@param sql string
+---@return string jsonData
+function freekill.SelectFromDb(db, sql)end
+
+---@param db freekill.SQLite3
+---@param sql string
+function freekill.ExecSQL(db, sql)end
+
+---@param db freekill.SQLite3
+function freekill.CloseDatabase(db)end