Before building our application, we must design a service API to cover the capabilities exposed by our middleware. We will design our API to be RESTful, as follows:

1. POST/login: Register a new user (administrative or ordinary) or log in as an existing one
2. POST/channel/create: Create a channel

3. POST/channel/join: Join the network peers to the channel created in this user's session
4. POST/chaincode/install: Install the chaincode on the peers
5. POST/chaincode/instantiate: Instantiate the chaincode on the channel
6. POST/chaincode/:fcn: Invoke the chaincode function fcn with passed arguments (in the body); examples for fcn are requestTrade, acceptLC, and so on
7. GET/chaincode/:fcn: Query the chaincode function fcn with passed arguments (in the body); examples for fcn are getTradeStatus, getLCStatus, and so on

Collectively, these API functions cover the transaction stages in Figure 5.3: The stages in the creation and operation of a blockchain application.