After identifying the resources, you work on the details of each API, that is, what is the input, the validation rules, the output, and status codes. You also need to specify the naming conventions and the data format. Once the details are fleshed out, you shouldn't go straight into the implementation phase. Instead, you should ask the developers of the clients of the API for feedback in order to see what you might have missed, and what further adjustments are required. One thing you should probably avoid is factoring in how the UI of the clients works into the API design consideration. How users interact with the UI of the clients of your API is irrelevant. You want to make the API generic so that it can be used for different types of clients.

Once you have finished the API's detail design, the design phase of the API is over. You then enter the implementation phase, which is what we will talk about in the next section.