GitLab's 403s on the MCP card, the catalog, and auth.md teach a cold agent that those files are forbidden. Then github.com serves no card, no catalog, and no Link header, while the working MCP sits in a vendor SDK the client already had hardcoded. The public web reads empty. The real server only exists for people who already knew the URL, so every new agent still gets the endpoint pasted in by hand. The card stays unpublished because the SDK already works, and the next client ships another hardcoded URL.