Custom MCPs: better error logging

Feedback
1

I’ve been working on creating custom MCP servers with fastMCP and noticed some current challenges with debugging issues:

  • The Tools & Integrations section of the Cursor settings will display the custom MCP server with a green dot and all of the server’s tools, but prompting the LLM in the chat for a list of servers will generally result in “no custom tools available”.
  • The MCP logs in the Output will show that the offerings are available (e.g., listOfferings: Found 8 tools), but still the LLM in the chat will state “no custom tools available”.
  • This issue occurs for i) configuring MCP servers in the global Cursor settings (~/.cursor/mcp.json) instead of per-project Cursor settings, regardless of stdio, sse, http, ii) if http is used instead of stdio, regardless of where the MCP servers are configured in the settings.

The lack of errors/warnings makes it quite challenging to debug why a custom MCP server is not actually available to LLMs in the chat.

I’m using fastMCP & Cursor v1.1.3