Can I use this with ChatGPT, Claude, AND Cursor, or just one?

All three, simultaneously, from the same MCP server. That’s the point of the protocol, one server, many clients. Claude Desktop: add an entry to ~/Library/Application Support/Claude/claude_desktop_config.json with the stdio command. ChatGPT custom connectors: expose the MCP server over HTTP/SSE (FastMCP supports this with one flag) and add the endpoint URL in ChatGPT’s Custom Connectors UI. Cursor: drop a .mcp.json in your project root with the command spec. Continue.dev, Cline, Zed: all speak MCP too. Build the server once, integrate everywhere. The MCP spec also lets you scope which tools each client can see, so Claude (your IDE) gets write tools and ChatGPT (a customer-facing assistant) gets read-only.