How to view MCP server logs for debugging

1# List all MCP log files
2ls -la ~/Library/Logs/Claude/mcp*.log
3
4# View the last 20 lines of all MCP logs
5tail -n 20 ~/Library/Logs/Claude/mcp*.log
6
7# Watch logs in real time (most useful for debugging)
8tail -n 20 -F ~/Library/Logs/Claude/mcp*.log
9
10# Search for errors in logs
11grep -i error ~/Library/Logs/Claude/mcp*.log | tail -20

1# PowerShell — list MCP log files
2Get-ChildItem "$env:APPDATA\Claude\logs\mcp*"
3
4# View last 20 lines
5Get-Content -Tail 20 "$env:APPDATA\Claude\logs\mcp*.log"
6
7# Watch in real time
8Get-Content -Tail 20 -Wait "$env:APPDATA\Claude\logs\mcp*.log"
9
10# Or open the folder in File Explorer
11explorer "$env:APPDATA\Claude\logs"

1# Steps to view MCP logs in Cursor:
2# 1. Open Output panel: View → Output (Cmd+Shift+U)
3# 2. Click the dropdown in the top-right of the Output panel
4# 3. Select 'MCP' or your specific server name
5# 4. Logs appear in real time as the server runs
6
7# You can also check the Developer Tools console:
8# Help → Toggle Developer Tools → Console tab
9# Filter for 'mcp' to see MCP-related messages

1// Useful logging patterns for MCP servers
2
3// Startup logging
4console.error(`[${new Date().toISOString()}] Server starting...`);
5console.error(`  Name: my-mcp-server`);
6console.error(`  Version: 1.0.0`);
7console.error(`  Node.js: ${process.version}`);
8console.error(`  API_KEY: ${process.env.API_KEY ? "SET" : "MISSING"}`);
9
10// Tool call logging (inside tool handler)
11console.error(`[${new Date().toISOString()}] Tool call: search`);
12console.error(`  Input: ${JSON.stringify(params)}`);
13const startTime = Date.now();
14// ... tool logic ...
15console.error(`  Duration: ${Date.now() - startTime}ms`);
16
17// Error logging
18console.error(`[${new Date().toISOString()}] ERROR in tool 'search':`);
19console.error(`  Message: ${error.message}`);
20console.error(`  Stack: ${error.stack}`);

1# Common log patterns and what they mean:
2
3# GOOD — Server started successfully:
4# "Server starting..."
5# "API_KEY: SET"
6# "MCP server connected and ready."
7
8# BAD — Missing dependency:
9# "Error: Cannot find module 'some-package'"
10# Fix: npm install some-package
11
12# BAD — Missing environment variable:
13# "FATAL: API_KEY environment variable is required"
14# Fix: Add API_KEY to your host config env block
15
16# BAD — Port already in use (HTTP transport):
17# "Error: listen EADDRINUSE :::3000"
18# Fix: Kill the other process on port 3000 or use a different port
19
20# BAD — Permission denied:
21# "Error: EACCES: permission denied, open '/path/to/file'"
22# Fix: Check file permissions or use a different path