How to derive data classes for any API

Let me be honest about a mistake I made this week.

I was building the data layer of a Pokedex app. I opened the JSON from the API, and I ended up writing two data classes for the list screen — PokemonListResponse and PokemonResult. And in my head, I invented a reason for why there were two.

"One of them," I told myself, "is the data coming from the server. The other one is the data I show in the UI."

It sounded smart. It was completely wrong.

Both classes describe the server's JSON. Neither one is "the UI data." I had looked at two classes and invented a structure that wasn't there — instead of reading the structure that actually was.