It’s not a new protocol.

It’s JSON-RPC plus OAuth.

(Plus a couple bits around managing a local server lifecycle.)

World would be surely a saner place if instead of “MCP vs CLI” people would talk about “JSON-RPC vs execlp(3)”.

Not accurate, but at least makes on think of the underlying semantics. Because, really, what matters is some DSL to discover and describe action invocations.