Cursor incorrectly filters out MCP tool names containing dots (.) and hyphens (-), despite being valid per MCP spec

Support Bug Reports
1

Where does the bug appear (feature/product)?

Cursor IDE

Describe the Bug

Cursor displays a warning for MCP tools whose names contain dot (.) characters, stating:

“Tool name must only contain alphanumeric characters and underscores”

However, the MCP specification (2025-11-25) explicitly lists the following as allowed characters in tool names (section 5.1.1 Tool Names):

The following SHOULD be the only allowed characters: uppercase and lowercase ASCII letters (A-Z, a-z), digits (0-9), underscore (_), hyphen (-), and dot (.)

The spec even includes admin.tools.list as an example of a valid tool name.

Steps to Reproduce

  • Install an MCP server that exposes tools with dots in their names (e.g., the webfuse-session-mcp server).
  • Connect to the server so it registers tools like act.click, see.domSnapshot, act.keyPress, etc.
  • Open the MCP Servers panel in Cursor.

Expected Behavior

All tools with spec-compliant names (containing dots and/or hyphens) should be listed without warnings and be fully usable.

Screenshots / Screen Recordings

Screenshot from 2026-04-14 15-55-16.png
Screenshot from 2026-04-14 15-55-16.png1889×775 135 KB

Operating System

Windows 10/11
MacOS
Linux

Version Information

Version: 3.0.16
VSCode Version: 1.105.1
Commit: 475871d112608994deb2e3065dfb7c6b0baa0c50
Date: 2026-04-09T05:33:51.767Z
Layout: editor
Build Type: Stable
Release Track: Default
Electron: 39.8.1
Chromium: 142.0.7444.265
Node.js: 22.22.1
V8: 14.2.231.22-electron.0
OS: Linux x64 6.17.9-76061709-generic

Does this stop you from using Cursor

No - Cursor works, but with this issue

5

Hey, thanks for the detailed report. I can see the screenshot with warnings for webfuse-session-mcp.

This is a confirmed bug. Tool name validation in Cursor currently doesn’t account for dots, even though the MCP spec explicitly allows them. On top of that, dots in names get replaced with underscores, so act.click becomes act_click, which can be confusing.

About the hyphens from the title, they’re already supported in the current version. The issue is specifically with dots.

I’ve passed this to the team. There’s no fix timeline yet, but your report helps with prioritization. Let me know if you hit any other issues because of this.