Documentation · MCP · Cursor

Debug browser bugs in Cursor — from real evidence

Cursor reads MCP servers from a JSON config file — project-level or global. One small file, and the agent can read every TraceBug export on your machine. Everything runs locally: the server is stdio-only, opens zero network connections, and reads report files from your disk. See the unedited transcript of Claude going from crash to root cause in five tool calls.

  1. 1

    Create the config file

    For one project, create .cursor/mcp.json in the project root. To make it available everywhere, put the same content in ~/.cursor/mcp.json instead.

    .cursor/mcp.json
    {
  "mcpServers": {
    "tracebug": {
      "command": "npx",
      "args": ["-y", "tracebug", "mcp"]
    }
  }
}
  2. 2

    Enable it

    Open Cursor Settings → MCP. The tracebug server should be listed — enable it if it isn't already, and check for the green status dot. Cursor may ask you to approve the server the first time the agent calls a tool.

  3. 3

    Capture a bug and ask

    Export a bug with the TraceBug extension, then tell Cursor's agent: "List my bug reports and investigate the newest one." The server auto-discovers exports in Downloads and Desktop; add "--dir", "./bug-reports" to the args array to pin a project folder.

Verify it worked

Settings → MCP shows tracebug with a green dot and six tools. In agent chat, ask "what MCP tools do you have?" and look for list_bug_reports.

Troubleshooting

Server shows a red/yellow status
Cursor launches the server with your shell's PATH — make sure npx (Node 18+) resolves. On Windows, fully restart Cursor after creating the file.
Agent ignores the tools
MCP tools are used by the Agent mode, not plain chat — make sure you're in agent/composer mode.
list_bug_reports returns nothing
Capture and Export .html first, or point --dir at the folder holding your exports.
No bug handy? Make one.
The live sandbox has intentional bugs — capture one, export it, and hand it to Cursor.
Open the sandbox

Full MCP reference — all six tools, the report format, and the FAQ — lives at /docs/mcp. Other tools: Claude Code · Windsurf.