I do sometimes wonder about the value of the whole MCP spec rather than just adding some semi-standard attributes to OpenAPI specs to make them more LLM consumable.

Seriously, it just makes no sense.

https://chatgpt.com/share/6abd1842-cd34-83e8-997e-55c8bc23cd...

"Just use OpenAPI" doesn't handle the question of having a single well-defined OAuth flow that will work with desktop clients across the board, as well as various gotchas like rendering embedded widgets that will use that OAuth flow, elicitations for user decision points outside of the model control, and other such things outside of the API round trip process itself.

Having built out MCP functionality for actual use cases for a small company, the big gotchas for us that can't be handled with "just an API" (putting aside the auth flow thing) have so far been (a) fully custom UI pieces in GUI clients (for example, media embeds with custom rendering) and (b) having the ability to put a user-facing hard stop in the loop for some interactions.

Part (a) in particular is pretty prominent for us since our uses cases are all about video, and having "just" an iframe URL to supply, with no other interaction with the model/turns, would give a pretty janky and unpleasant experience if Claude/ChatGPT even allowed it to embed.