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How to fix: MCP server not connecting / tools not showing up

Last verified: June 2026· Claude Code, Cursor, and other MCP clients

Where this shows up

Claude Code, Cursor, and other MCP clients

The fix

  1. 1Verify the server config in your client (command/URL, transport type) matches what the server expects.
  2. 2Check authentication — many hosted MCP servers need OAuth, not a plain API key; the two are different auth systems.
  3. 3Confirm the server is actually running and reachable from the client’s environment (network/firewall).
  4. 4Restart the client after config changes so it re-discovers the server’s tools.
  5. 5Read the server logs — most connection failures are auth or transport mismatches that the logs name directly.

Prevent it

Use a well-built MCP server with clear auth, health checks, and logging so connection issues are obvious and rare.

Common variations and related errors

You'll usually hit this same root cause under a few different names. Same fix.

  • "MCP server not found"
  • "tool not available"
  • "spawn ENOENT"
  • "connection refused"
  • "401 from MCP server"
  • "OAuth callback failed"
  • "MCP transport error"

Frequently asked questions

What causes “MCP server not connecting / tools not showing up”?

The server config, transport, or auth is misconfigured, so the client can’t reach or authenticate to the MCP server.

How do I prevent “MCP server not connecting / tools not showing up” from recurring?

Use a well-built MCP server with clear auth, health checks, and logging so connection issues are obvious and rare.