[rswail]

I'm glad you haven't described your API as RESTful.

You're perfectly fine to design an API around RPC calls and POST. There are all of the issues around RPC that you will have to deal with (long running operations, versioning, serde and marshalling of arguments, argument and response typing and interface definitions, codegen of the IDL to product client and server stubs that will require modification and back/forward porting of implementation).

But an API definition like this one, covers a lot of that as part of the protocol, most of which is defined by HTTP anyway. You also get encryption, compression, caching, tooling "for free".