The user experience for a rest api and for mcp can be the same. For MCP, you have to give the mcp server url. For REST, you could provide a url to the openapi spec. The open API spec has everything you'd need - oauth url + all the endpoints and params.

Most chat products will just have a directory of connectors anyways - so for non technical folks they won't even here the term MCP or REST, they'll just "Install the Gmail plugin".