I have done it many times, using the swagger.json as a "discovery service" and then having the agent utilize that API. A good OpenAPI spec was working perfectly fine for me all the way back when OpenAI introduced GPTs.
If we standardized on a discovery/ endpoint, or something like that, as a more compact description of the API to reduce token usage compared to consuming the somewhat bloated full OpenAPI spec, you would have everything you need right there.
The MCP side quest for AI has been one of the most annoying things in AI in recent years. Complete waste of time.
I consider it a good first attempt, but indeed hope for a sort of mcp2.0
Swagger/OpenAPI is "this is EXACTLY what the API does, if you don't do it like this, you will fail". If you change something, things will start falling apart.
Because of FOMO a lot of higher up decided that "we must do a MCP to show that we're also part of the cool kids" and to give an answer to their even-higher-up about "What are you doing regarding IA ?"
The project has been approved, a lot of time has been sunk into the project, so nobody wants to admit that "hmmm actually now it's irrelevant our existing API + a skill.md is enough"
I've seen that in at least 4 companies my friends work in, so I would be surprised if it's not something like that here too.
On the contrary claude code, in my experience, has been perfectly able to use `stripe` `gh` and to construct on the fly a figma cli (once instructed to do it).