this guide is just for an example of how to build a single mcp (e.g. a vector store). chatgpt connectors implement mcps in general now
Cause from TFA “To work with ChatGPT Connectors or deep research (in ChatGPT or via API), your MCP server must implement two tools - search and fetch.”
Also, this page is actually the only docs site about MCP they have, and their help articles link to it too.