MCP connection problems
Diagnose an unreachable upstream server or failing wrapped endpoint.
The upstream connection fails
If Gooshi says it "could not negotiate a supported modern or legacy Streamable HTTP MCP protocol," it did not receive a usable MCP response. That message can be caused by reachability, URL, authentication, HTTP response, or actual protocol negotiation—not only by the protocol version.
Check:
- The URL is the current public HTTPS endpoint and includes the MCP path,
usually
/mcp. - The endpoint is reachable outside the MCP Owner's private network.
- TLS is valid.
- The endpoint accepts Streamable HTTP POST requests rather than returning an HTML page, redirect loop, or ordinary website response.
- Required access details are present in the supported connection fields.
- The upstream service is healthy.
Temporary tunnel URLs deserve a separate check. After restarting the computer,
restart both the upstream MCP server and its tunnel. If the tunnel was recreated,
copy its new public hostname into Gooshi; an older trycloudflare.com address no
longer points to the current server. Then retry connection and tool discovery.
Common clues:
| Symptom | Check next |
|---|---|
| 404 or an HTML page | The missing or incorrect /mcp path |
| 401 or 403 | Upstream authentication and allowed headers |
| Timeout or unreachable host | Upstream process, tunnel process, firewall, and current hostname |
| JSON-RPC response but negotiation still fails | Streamable HTTP support and advertised MCP version |
Do not paste credentials into a support request.
The wrapped endpoint fails in a client
- Copy the endpoint again from the MCP server's Test section.
- Confirm the client supports remote MCP connections.
- Start a clean client session.
- Try a simple discovered tool with safe input.
- Review Activity for a corresponding event.
Test each client type separately. If only one client fails, include its name and version in your support request.