Cursor refuses to use my MCP server

[user8972]

I developed an MCP server which publishes one tool. The MCP server is correctly added into the settings and able to be reached by Cursor, as evidenced by the fact the one tool is correctly discovered and listed under the settings (see screenshot).

Everything works in Claude Desktop.

Yet I can’t seem to trigger Cursor to actually use the tool.

Even when I specifically ask Cursor to run the tool by its name, it never does it and instead answers based on the underlying model’s training (in this case Claude).

Composer (in agent mode):

Me: According to the search-my-docs MCP tool, what is the latest version of tailwindcss?

Let me search through the files to find information about the tailwindcss version.

I apologize, but I don’t have access to the search-my-docs MCP tool or its data in this environment. Without access to that specific tool or documentation, I cannot tell you what version of tailwindcss it references.

If you’d like to know the latest version of tailwindcss, I’d recommend:

1. Checking the official tailwindcss website (https://tailwindcss.com)
2. Looking at the npm package page (tailwindcss - npm)
3. Or checking your project’s package.json file if you have tailwindcss installed

Would you like me to help you find this information in any of these ways?

[OssianRavn]

I lost access to command mcp running locally in the middle of a session yesterday. Haven’t had it since. When I request Cursor/Sonnet to use MCP it obviously doesn’t know what I am referring to.

I’m quite sure something was changed in the system prompt yesterday and MCP tools were made unavailable. If only there was some transparency.

[shuntaka9576]

The same issue occurs in my environment.

$ cursor --version
0.45.11
f5f18731406b73244e0558ee7716d77c8096d150
arm64

The tools/json file is as follows:

src/core/mcp/tools.json

[domasm92]

Try using underscores (_) instead of dashes (-) in the name. It think Cursor doesn’t recognize tools with dashes. Although it worked until yesterday, I had my selfmade MCP working with dashes

[johnnyhoang9]

Thanks! I got it to finally work by removing the dashes from my tool names

[MaxKless]

Same, using underscores instead of dashes fixed it for me.

[ninesunsabiu]

Yes. I have some problem.
but I using underscores instead of dashes fixed it for me too

[LanfordCai]

Same here, have no idea how to fix this…

[MaxKless]

try on the latest version of cursor and make sure you’re in agent mode

[webdevtodayjason]

I am having the same issues. Cursor is in agent mode, claude 3.7.
Both servers I have work in Claude Desktop. The AI refuses to believe it can have tools. I have tried so many ways. Yes the tools have underscores. =)
-J

[webdevtodayjason]

Maybe it believes a picture. =)

haha nope.

What should I try next?

-J

[loitragg]

Same here. Agent mode and claude sonnet 3.7, it doesn’t recognize these tools. But it works well with Claude Desktop.

As you can see those tool names are using underscore and no dash. But Cursor still doesn’t give it a shoot.