OpenAPI doesn't have a baked in discoverability mechanism. It isn't compatible with LLMs out of the box. It is a lower level abstraction. I don't want to write a blob of code that talks to an Open API service every time I want to do something with an LLM.
>OpenAPI doesn't have a baked in discoverability mechanism.
Well, Swagger was there from the start, and there's nothing stopping an LLM from connecting to an openapi.json/swagger.yaml endpoint, perhaps meditated by a small xslt-like filter that would make it more concise.