There is. See here. IDK how good the API documentation is (haven't checked), but it should be linked in that page.

Absolutely!

https://join-lemmy.org/api/classes/LemmyHttp.html

This is the wrong community for this question, it's an open-ended discussion forum like AskReddit... not a support forum for Lemmy.

That said, check out the v18 API before you start writing a bot. It's going to change in a big way shortly.

There's a JS client, or you can generate one from the OpenAPI spec I put together: https://github.com/Stumblinbear/lemmy-openapi

https://join-lemmy.org/docs/en/contributors/04-api.html

There's an API, and generated JS bindings, and docs generated from those JS bindings.

I was planning on looking into generating generic docs or C# bindings from the server Rust code annotations that are being used for generating the JS bindings.

For now, you can try that, or orient yourself on the JS docs even if you won't use JS.

There's got to be for apps like Jerboa to work.