Yes, MCP is an API.
Previously, it was an API with a weird stateful standard; now it is essentially a bog-standard stateless JSON-RPC API with conventions for tool discovery, long-running tasks and multi-round-trip requests
If you wrote your own JSON-RPC API for an LLM, you would probably eventually end up with something that looks very much like the standard they're describing.
Ahh so it's the 2025 name for CORBA? just kidding, I meant SOA /s
But your answer is the first one that seems to be relevant, so thank you.