diff --git a/Engine/Public/Attributes/LCEngineClassHookAttribute.cs b/Engine/Public/Attributes/LCEngineClassHookAttribute.cs
index 6fbe6d8..e62aee0 100644
--- a/Engine/Public/Attributes/LCEngineClassHookAttribute.cs
+++ b/Engine/Public/Attributes/LCEngineClassHookAttribute.cs
@@ -10,6 +10,10 @@ namespace LeanCloud.Engine {
         AfterDelete
     }
 
+    /// <summary>
+    /// LCEngineClassHookAttribute is an attribute that hooks class in engine.
+    /// </summary>
+    [AttributeUsage(AttributeTargets.Method, AllowMultiple = false)]
     public class LCEngineClassHookAttribute : Attribute {
         public string ClassName {
             get;
diff --git a/Engine/Public/Attributes/LCEngineFunctionAttribute.cs b/Engine/Public/Attributes/LCEngineFunctionAttribute.cs
index 1f4ddb0..59ce4be 100644
--- a/Engine/Public/Attributes/LCEngineFunctionAttribute.cs
+++ b/Engine/Public/Attributes/LCEngineFunctionAttribute.cs
@@ -1,6 +1,9 @@
 using System;
 
 namespace LeanCloud.Engine {
+    /// <summary>
+    /// LCEngineFunctionAttribute is an attribute of cloud function in engine.
+    /// </summary>
     [AttributeUsage(AttributeTargets.Method, AllowMultiple = false)]
     public class LCEngineFunctionAttribute : Attribute {
         public string FunctionName {
diff --git a/Engine/Public/Attributes/LCEngineFunctionParamAttribute.cs b/Engine/Public/Attributes/LCEngineFunctionParamAttribute.cs
index 157608c..c762380 100644
--- a/Engine/Public/Attributes/LCEngineFunctionParamAttribute.cs
+++ b/Engine/Public/Attributes/LCEngineFunctionParamAttribute.cs
@@ -1,6 +1,9 @@
 using System;
 
 namespace LeanCloud.Engine {
+    /// <summary>
+    /// LCEngineFunctionParamAttribute is an attribute of the parameter of cloud function in engine.
+    /// </summary>
     [AttributeUsage(AttributeTargets.Parameter, AllowMultiple = false)]
     public class LCEngineFunctionParamAttribute : Attribute {
         public string ParamName {
diff --git a/Engine/Public/Attributes/LCEngineRealtimeHookAttribute.cs b/Engine/Public/Attributes/LCEngineRealtimeHookAttribute.cs
index 8c23d06..b8ea596 100644
--- a/Engine/Public/Attributes/LCEngineRealtimeHookAttribute.cs
+++ b/Engine/Public/Attributes/LCEngineRealtimeHookAttribute.cs
@@ -20,6 +20,10 @@ namespace LeanCloud.Engine {
         ClientOffline,
     }
 
+    /// <summary>
+    /// LCEngineRealtimeHookAttribute is an attribute that hooks realtime in engine.
+    /// </summary>
+    [AttributeUsage(AttributeTargets.Method, AllowMultiple = false)]
     public class LCEngineRealtimeHookAttribute : Attribute {
         public LCEngineRealtimeHookType HookType {
             get;
diff --git a/Engine/Public/Attributes/LCEngineUserHookAttribute.cs b/Engine/Public/Attributes/LCEngineUserHookAttribute.cs
index c9485f1..bf5e25d 100644
--- a/Engine/Public/Attributes/LCEngineUserHookAttribute.cs
+++ b/Engine/Public/Attributes/LCEngineUserHookAttribute.cs
@@ -7,6 +7,10 @@ namespace LeanCloud.Engine {
         OnLogin
     }
 
+    /// <summary>
+    /// LCEngineUserHookAttribute is an attribute that hooks user in engine.
+    /// </summary>
+    [AttributeUsage(AttributeTargets.Method, AllowMultiple = false)]
     public class LCEngineUserHookAttribute : Attribute {
         public LCEngineUserHookType HookType {
             get;
diff --git a/Engine/Public/LCEngine.cs b/Engine/Public/LCEngine.cs
index a71368e..0a7bc4d 100644
--- a/Engine/Public/LCEngine.cs
+++ b/Engine/Public/LCEngine.cs
@@ -11,6 +11,9 @@ using Microsoft.Extensions.DependencyInjection;
 using LeanCloud.Common;
 
 namespace LeanCloud.Engine {
+    /// <summary>
+    /// LCEngine provides the initialization of Engine in LeanCloud.
+    /// </summary>
     public class LCEngine {
         public const string LCEngineCORS = "LCEngineCORS";
 
@@ -79,6 +82,10 @@ namespace LeanCloud.Engine {
         public static Dictionary<string, MethodInfo> ClassHooks = new Dictionary<string, MethodInfo>();
         public static Dictionary<string, MethodInfo> UserHooks = new Dictionary<string, MethodInfo>();
 
+        /// <summary>
+        /// Initializes the engine with the given services.
+        /// </summary>
+        /// <param name="services"></param>
         public static void Initialize(IServiceCollection services) {
             // 获取环境变量
             LCLogger.Debug("-------------------------------------------------");
@@ -198,7 +205,7 @@ namespace LeanCloud.Engine {
             });
         }
 
-        public static void PrintEnvironmentVar(string key) {
+        private static void PrintEnvironmentVar(string key) {
             LCLogger.Debug($"{key} : {Environment.GetEnvironmentVariable(key)}");
         }
 
@@ -293,7 +300,7 @@ namespace LeanCloud.Engine {
             }
         }
 
-        public static object GetFunctions(HttpRequest request) {
+        internal static object GetFunctions(HttpRequest request) {
             CheckMasterKey(request);
 
             List<string> functions = new List<string>();
diff --git a/Engine/Public/LCEngineRequestContext.cs b/Engine/Public/LCEngineRequestContext.cs
index c04c2f9..68e9e2f 100644
--- a/Engine/Public/LCEngineRequestContext.cs
+++ b/Engine/Public/LCEngineRequestContext.cs
@@ -1,9 +1,11 @@
-using System;
-using System.Collections.Generic;
+using System.Collections.Generic;
 using System.Threading;
 using LeanCloud.Storage;
 
 namespace LeanCloud.Engine {
+    /// <summary>
+    /// LCEngineRequestContext provides the context of engine request.
+    /// </summary>
     public class LCEngineRequestContext {
         public const string RemoteAddressKey = "__remoteAddressKey";
         public const string SessionTokenKey = "__sessionToken";
@@ -31,7 +33,10 @@ namespace LeanCloud.Engine {
             }
             return requestContext.Value[key];
         }
-        
+
+        /// <summary>
+        /// The remote address of this request.
+        /// </summary>
         public static string RemoteAddress {
             get {
                 object remoteAddress = Get(RemoteAddressKey);
@@ -45,6 +50,9 @@ namespace LeanCloud.Engine {
             }
         }
 
+        /// <summary>
+        /// The session token of this request.
+        /// </summary>
         public static string SessionToken {
             get {
                 object sessionToken = Get(SessionTokenKey);
@@ -58,6 +66,9 @@ namespace LeanCloud.Engine {
             }
         }
 
+        /// <summary>
+        /// The user of this request.
+        /// </summary>
         public static LCUser CurrentUser {
             get {
                 object currentUser = Get(CurrentUserKey);
diff --git a/Storage/Storage/Public/LCCloud.cs b/Storage/Storage/Public/LCCloud.cs
index a5dcb01..91d671e 100644
--- a/Storage/Storage/Public/LCCloud.cs
+++ b/Storage/Storage/Public/LCCloud.cs
@@ -6,7 +6,8 @@ using LeanCloud.Storage.Internal.Object;
 
 namespace LeanCloud.Storage {
     /// <summary>
-    /// LeanEngine
+    /// LCCloud contains static functions that call the cloud functions of Engine
+    /// in LeanCloud.
     /// </summary>
     public static class LCCloud {
         private const string PRODUCTION_KEY = "X-LC-Prod";