I developed several MCP servers that expose params of varying types. I configured Cursor to use these MCP servers via stdin.
Cursor cannot discover and call my MCP tools, but cannot apply any of the parameters their endpoints expose. It so happens all my MCP endpoints have default behavior that lets them work without the params set, so Cursor always tries with an optional param, the falls back to the no-param call. However, some of my more recent MCP endpoints REALLY need those params passed in many scenarios.
I’ve attached screenshots showing:
- One of my MCP server endpoints with an optional int param
- The error Cursor always throws when calling it (then calls it without any params)
- A screenshot showing the MCP inspector console calling that same MCP endpoint WITH that same param successfully
Cursor Desktop can also call these MCP endpoints with the params.
The Cursor issue is consistent across all my MCP servers and endpoints. Cursor cannot use their params. I believe it to be a Cursor but, since no other MCP client has this issue with these same MCP servers.
I do not know whether this is because the params are optional, since ALL my params currently are optional.
I’m on MacOS Sierra.
Cursor Version: 0.45.15
To reproduce you’ll need to create or find an MCP server with endpoints that accept params, preferably optional ones for comparison. Recommend a non-string type, as it may be related to typing. Try to get Cursor to pass a value for one of the params.
