diff --git a/zenlink-protocol/rpc/Cargo.toml b/zenlink-protocol/rpc/Cargo.toml
index 8004aa8..c45d79a 100644
--- a/zenlink-protocol/rpc/Cargo.toml
+++ b/zenlink-protocol/rpc/Cargo.toml
@@ -3,6 +3,7 @@ name = "zenlink-protocol-rpc"
 version = "0.4.0"
 authors = ["Zenlink Developers"]
 edition = "2018"
+license = "GPL-3.0-only"
 
 [package.metadata.docs.rs]
 targets = ['x86_64-unknown-linux-gnu']
diff --git a/zenlink-protocol/rpc/README.md b/zenlink-protocol/rpc/README.md
index 5c33988..c7cfa8e 100644
--- a/zenlink-protocol/rpc/README.md
+++ b/zenlink-protocol/rpc/README.md
@@ -541,3 +541,7 @@
   }
 }
 ```
+
+## License
+
+[GPL-v3](LICENSE)
diff --git a/zenlink-protocol/rpc/runtime-api/Cargo.toml b/zenlink-protocol/rpc/runtime-api/Cargo.toml
index 02f2a4e..02196ec 100644
--- a/zenlink-protocol/rpc/runtime-api/Cargo.toml
+++ b/zenlink-protocol/rpc/runtime-api/Cargo.toml
@@ -3,6 +3,7 @@ name = "zenlink-protocol-runtime-api"
 version = "0.4.0"
 authors = ["Zenlink Developers"]
 edition = "2018"
+license = "GPL-3.0-only"
 
 [dependencies]
 # alias "parity-scale-code" to "codec"
diff --git a/zenlink-protocol/src/README.md b/zenlink-protocol/src/README.md
new file mode 100644
index 0000000..65ca6f0
--- /dev/null
+++ b/zenlink-protocol/src/README.md
@@ -0,0 +1,100 @@
+## Zenlink Protocol v0.4.0 Overview
+![zenlink protocol](./docs/zenlink-protocol-v0.4.0.png)
+
+`Zenlink Protocol` mainly consists of two parts: assets and asset operations, 
+namely `Zenlink Assets` and `Zenlink Actions`.
+Through the `UAI`(unified asset identifier) and `MultiAssetsHandler` interfaces, 
+`Zenlink` can perform `Swap` and `Transfer By XCM` any asset on the chain.
+
+## Zenlink Protocol v0.4.0 Features
+- Based on the `newest` XCM design
+- Based on `FRAMEv2`
+- Swap exchange fee `configurable`
+- `Compatible` Polkadot XCMP cross-chain asset processing
+- Zenlink Protocol registration whitelist-XCM `trust collection management`
+- Through Transfer-By-XCM, `assets can flow freely` between parachains
+- ZenlinkMultiAssets adapter comes with `LIQUIDITY` and `Foreign` asset processing, which can `adapt to various native assets such as NATIVE/LOCAL/RESERVE`
+- Provide LocalAssetHandler, OtherAssetHandler and other traits to `support locally defined assets such as LOCAL and RESERVE`
+- Under the control of MultiAssetsHandler, `assets can swap freely`
+
+##  UAI v0.1.0
+
+- UAI v0.1.0 definition
+
+```rust
+pub struct AssetId {
+    pub chain_id: u32, // ParaId
+    pub asset_type: u8, // Asset types supported by Zenlink Assets
+    pub asset_index: u32, // the index number of the asset
+}
+```
+
+- UAI v0.1.0 asset type
+
+`asset_type` currently only supports the following values:
+
+```rust
+/// Native currency, the most basic asset on each parachain
+pub const NATIVE: u8 = 0;
+/// Swap module asset, LP token generated by Zenlink DEX
+pub const LIQUIDITY: u8 = 1;
+/// Other asset type on this chain, other asset modules on this chain
+pub const LOCAL: u8 = 2;
+/// Reserved for future, reserved asset type
+pub const RESERVED: u8 = 3;
+```
+
+In the current version of UAI, `Zenlink Assets` supports up to four locally defined assets of `Native/LIQUIDITY/LOCAL/RESERVED`.
+When these four assets are transferred across chains, a cross-chain mapping asset category `Foreign` will be generated inside `ZenlinkProtocol`.
+
+- `Before and after the cross-chain asset transfer, the UAI of the asset has not changed`.
+
+## MultiAssetsHandler
+
+The trait is defined as follows
+```rust
+pub trait MultiAssetsHandler<AccountId> {
+    fn balance_of(asset_id: AssetId, who: &AccountId) -> AssetBalance;
+    fn total_supply(asset_id: AssetId) -> AssetBalance;
+    fn is_exists(asset_id: AssetId) -> bool;
+    fn transfer(
+        asset_id: AssetId,
+        origin: &AccountId,
+        target: &AccountId,
+        amount: AssetBalance,
+    ) -> DispatchResult {
+        let withdrawn = Self::withdraw(asset_id, origin, amount)?;
+        let _ = Self::deposit(asset_id, target, withdrawn)?;
+        Ok(())
+    }
+    fn deposit(
+        asset_id: AssetId,
+        target: &AccountId,
+        amount: AssetBalance,
+    ) -> Result<AssetBalance, DispatchError>;
+
+    fn withdraw(
+        asset_id: AssetId,
+        origin: &AccountId,
+        amount: AssetBalance,
+    ) -> Result<AssetBalance, DispatchError>;
+}
+
+```
+
+- `is_exists` is a unified access interface for `Zenlink Actions`
+- `balance_of`, `total_supply`, `transfer` are `Zenlink Swap Action` access interface
+- `deposit`, `withdraw` are `Zenlink Transfer-By-XCM Action` access interface
+- `MultiAssetsHandler` can operate in addition to the four native defined assets identified by `UAI`, 
+as well as the `cross-chain mapping asset Foreign` inside `ZenlinkProtocol`.
+
+
+## Swap and Transfer-By-XCM
+- Four native defined assets (`NATIVE/LIQUIDITY/LOCAL/RESERVED`) and cross-chain mapping assets (`Foreign`) can be exchanged through `MultiAssetsHandler`.
+- Four native defined assets (`NATIVE/LIQUIDITY/LOCAL/RESERVED`) Cross-chain asset transfer through `Transfer-By-XCM`, and a mapped asset `Foreign` is generated 
+on the target parachain, Also through the `Transfer-By-XCM` cross-chain transfer back to the original definition chain of the asset.
+
+
+## License
+
+[GPL-v3](LICENSE)
diff --git a/zenlink-protocol/src/docs/zenlink-protocol-v0.4.0.png b/zenlink-protocol/src/docs/zenlink-protocol-v0.4.0.png
new file mode 100644
index 0000000..1992609
Binary files /dev/null and b/zenlink-protocol/src/docs/zenlink-protocol-v0.4.0.png differ
diff --git a/zenlink-protocol/src/transfer/mod.rs b/zenlink-protocol/src/transfer/mod.rs
index 5ac447b..545b3ee 100644
--- a/zenlink-protocol/src/transfer/mod.rs
+++ b/zenlink-protocol/src/transfer/mod.rs
@@ -1,3 +1,6 @@
+// Copyright 2020-2021 Zenlink
+// Licensed under GPL-3.0.
+
 use super::*;
 
 impl<T: Config> Pallet<T> {