It works just fine until I updated to the latest version of cursor
Using mcp inspector, the mcp server also returns correct result.
Could it be a bug?
Me too. ALL mcp tools stopped working about an hour ago.
The agent is unable to send any parameters through to the tools, so all calls fail.
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Ran into the same issue - Cursor recognizes MCP servers but canât actually call a tool
Same here, even though I didnât update the client
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ME too - Iâm on:
Version: 0.48.2 (user setup)
VSCode Version: 1.96.2
Commit: 7d6318dfcfbf7c12a87e33c06978f23167a6de30
Date: 2025-03-26T02:54:05.125Z
Electron: 34.3.4
Chromium: 132.0.6834.210
Node.js: 20.18.3
V8: 13.2.152.41-electron.0
OS: Windows_NT x64 10.0.26100
By mad co-incidence, I had the devtools tab open, and I had un-blocked the console.log output, so I was able to see that cursor itself suddenly started showing âmcp parse erorrsâ over-and-over.
Same here, stopped about an hour ago for me. Using the exact same mcp json file for Visual Studio Code and they all work fine in there.
As an MCP author, this scares the â â â â out of me since I didnât even release an update yet, lmao.
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Yeap same here. Happened on todayâs update. No more mcp tools. Very sad. 
Iâm on early access.
Happened to me yesterday; turns out it was related to my npx/npm configs and not Cursor. It started ârandomlyâ (I hadnât changed anything related to MCPs or npx).
You will need to completely uninstall and reinstall the MCP packges that use npx. I think I also had to globally install the packages (via npm) but I could be misremembering, try this if a fresh install doesnât work.
I also changed some of the MCP commands to use uvx (instead of npx), though I donât think this is necessary after doing the above step.
If this doesnât fix the issue please reply to my comment and Iâll look through my terminal history to see if I did anything else to fix it.
MCP author here. Confirming that all my users are seeing this as well. Odd that it seems to have started happening without any client-side update required?
Same here.
Yeah Cursor team will have to look into this as it is likely update related and a very specific error.
Lets give them time to check it out. It has been checked here by MCP authors and users.
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Are we all windows users, or does this affect Mac as well?
Mac user here.
Yes, me.
Some user posted that they have same on earlier versions so it may be cursor tool call processing.
Same here.
Same, not using early access.
Cross checked the MCP tool (sequential thinking) if its working on Claude and it does.
Hopefully gets fixed soon
Same here. Iâm using v0.48.5