If you want to use stable diffusion t2i and i2i today via an self-hosted api it's very easy to do so with auto1111, just click the api link at the bottom of the gradio app and there's extensive documentation on the endpoints.

I think it can only use other APIs itself. Looks like they want to make it work with a1111's api and they will ship a plugin that talks to stability's pay api.

Did you miss the large API link in the header?

Unkind response, and the API link goes to info about Stability's API, not info about an API for interacting with the StableStudio app.

You don't use APIs to interact with apps. Apps use APIs to do actions.