API documentation / types / signature is just one of the four types of documentation[1] that every service and library should ship. The other three are for telling people the things that code cannot tell you. The OP is arguing that the only "docs" you need are "how do I call this", not "what does this do", or "what do I do with the results", among plenty of others.

So no, what the author should be writing is "Ship Types and Docs".

[1] https://diataxis.fr/

What about using LLMs to automatically update docs?

so like GraphQL?