I guarantee you any LLM will be perfectly capable of navigating HTTP auth [1] which has been around since 1999.

You could use `curl`, or you could bake an HTTP client tool into the agent harness which operates at a more abstract level. The agent would just have a tool that looks a lot like the Fetch API [2] and the harness could simply be configured to inject credentials using the various well-established patterns that have long existed, allow / deny certain methods, etc. The thing is, everything you can do with MCP could also simply be done with REST, so neither is inherently better than the other, I just don't like the proliferation of needless standards.

[1]: https://developer.mozilla.org/en-US/docs/Web/HTTP/Guides/Aut...

[2]: https://developer.mozilla.org/en-US/docs/Web/API/Fetch_API/U...