The -32601 method not found error means your MCP client reached a server, but asked for a method the server does not expose.

This usually happens when:

• client and server are using different protocol versions
• server method names do not match the MCP transport handler
• request routing points to the wrong endpoint
• a proxy strips or rewrites JSON-RPC payloads

Fast diagnosis checklist

1. Confirm endpoint responds to MCP handshake in Playground
2. Verify your server returns tools/list and expected method names
3. Ensure JSON-RPC method field is exact and case-sensitive
4. Check reverse proxy rules for request body rewriting
5. Test with the same headers your IDE sends

Common fix patterns

1) Wrong transport route

If your IDE is configured for SSE but endpoint expects HTTP JSON-RPC, you can get -32601.

• verify route and transport in your client config
• use the exact endpoint URL documented by your server

2) Method namespace mismatch

If server expects namespaced methods and client sends short names, method lookup fails.

jsonCOPY
{
  "jsonrpc": "2.0",
  "id": 1,
  "method": "tools/list"
}

Validate the expected method set in your server docs and implementation.

3) Old client schema cache

Some IDE extensions keep old method catalogs.

• restart IDE
• remove and re-add server config
• run a fresh probe in Playground

How to verify fix

• Run endpoint probe in Playground
• Confirm is_mcp: true
• Confirm tool_count > 0
• Reconnect from IDE and run one known-safe tool call

If methods still fail, compare raw request and response side by side using server logs.

Related troubleshooting

• MCP error connection closed (-32000)
• No working IDE endpoint available
• MCP server not working guide