Retrofit for Unity is a plugin that turn your REST / RESTful APIs into interface.
Document
If you are looking for a plugin that help you maintain and use your HTTP APIs gracefully. Retrofit for Unity is a tool out of box for you. There are six built-in methods: GET, POST, PUT, DELETE, PATCH and HEAD.
Retrofit for Unity is just a reformatted code style to request a HTTP API.
It doesn’t send a real HTTP Request in its module, which means you can integrated Retrofit for Unity with different HTTP Plugins or Unity Official UnityWebRequest system.
By default, it provides three integrations to send HTTP request, which are WWWRequestImpl, UnityWebRequestImpl and BestHttpImpl.