MCP Logging Issue

Discussions
1

Wondering if anyone can point me to how to get logging in my MCP server.
When I run in manually with node it all works fine. But when I point the IDE at it the logging does not come through. I presume cursor is spinning up a virtual environment or something and the log directory is in there instead.

hard to debug anything without it.

Running as :
Command
node C:\git\mcp-template\dist\index.js

2nd Q
Is there a way to programmatically add the configs? I know about the project level MCP but more after global config. I searched everywhere but seems to be internal to the IDE?

1 Like
2

Plus one on this. Where are the MCP logs? I get an infinite generation message and no insight into issues.

3

Part of my .cursorrules:

Locating Cursor MCP Logs

When MCP fails, follow these steps to locate and analyze the logs:

  1. Primary MCP Log Location:

    ~/Library/Application Support/Cursor/logs/[SESSION_ID]/window[N]/exthost/anysphere.cursor-always-local/Cursor MCP.log

    Where:

    • [SESSION_ID] is a timestamp-based directory like “20250313T140544”
    • [N] is the window number (1, 2, 3, etc.)

  2. Session Directories:

    • Log sessions are organized by date in directories with format: YYYYMMDDTHHMMSS
    • The most recent sessions are the ones with the latest timestamps
    • Example: ~/Library/Application Support/Cursor/logs/20250313T140544/

  3. Related Log Files:

    • Filesync logs: window[N]/exthost/anysphere.cursor-always-local/Filesync.log
    • Retrieval logs: window[N]/exthost/anysphere.cursor-retrieval/Cursor Indexing & Retrieval.log
    • Window renderer logs: window[N]/renderer.log

Common MCP Error Patterns

  1. JSON Parsing Errors:

    • Look for: Client error for command '/path/to/script': Unexpected token 'X', "..." is not valid JSON
    • Cause: MCP scripts outputting non-JSON text that Cursor expects to be JSON
    • Fix: Ensure your script outputs only valid JSON when communicating with Cursor

  2. Connection Errors:

    • Look for: Error connecting to MCP server or Connection refused
    • Cause: MCP server script not running or permissions issues
    • Fix: Check script permissions, execution state, network connectivity

  3. Tool Execution Errors:

    • Look for: Failed to execute tool 'tool_name'
    • Cause: Internal errors in MCP tool implementation
    • Fix: Debug the tool code, check parameter parsing

Manual Log Analysis Commands

Use these terminal commands to search for errors:

  1. Find recent error logs:

    find ~/Library/Application\ Support/Cursor/logs -type f -name "Cursor MCP.log" -mtime -3 | xargs grep -l "\[error\]"

  2. Find errors for specific MCP server:

    find ~/Library/Application\ Support/Cursor/logs -type f -name "Cursor MCP.log" | xargs grep -l "jira-final" | xargs grep "\[error\]"

  3. View full context of errors:

    grep -A 5 -B 2 "\[error\]" [path-to-specific-log-file]

  4. Check successful tool calls for comparison:

    grep "Successfully called tool" [path-to-specific-log-file]
3 Likes
4

Thank you so much for this!