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Debug MCP server communication. Use for troubleshooting MCP integrations, viewing traffic, and analyzing latency.
npx skill4agent add johnlindquist/claude mcp-spy# Check MCP logs
tail -f ~/.claude/debug/mcp-*.log
# Or specific server
tail -f ~/.claude/debug/mcp-cm.log# Tool calls only
grep "tool_use" ~/.claude/debug/mcp-*.log
# Errors only
grep -i "error\|failed" ~/.claude/debug/mcp-*.log
# Specific tool
grep "beads_add" ~/.claude/debug/mcp-*.log# Time a specific tool
time claude --print "Run beads_ready" --dangerously-skip-permissions 2>&1 | head -1# Look for latency warnings in logs
grep -i "timeout\|slow\|latency" ~/.claude/debug/mcp-*.log# All errors
grep -i "error" ~/.claude/debug/mcp-*.log
# Parse error responses
grep "\"error\":" ~/.claude/debug/mcp-*.log | jq '.'# Test server connection
curl -X POST http://localhost:3000/mcp/list_tools \
-H "Content-Type: application/json" \
-d '{}'# View server logs (if running as process)
tail -f logs/mcp-server.log
# Or in terminal running server
# Logs appear in stdout# Call tool directly
curl -X POST http://localhost:3000/mcp/call_tool \
-H "Content-Type: application/json" \
-d '{
"name": "beads_ready",
"args": {}
}'# Pretty print JSON messages
grep "message" ~/.claude/debug/mcp-*.log | jq '.'# Check request format
gemini -m pro -o text -e "" "Validate this MCP request format:
$(grep "request" ~/.claude/debug/mcp-*.log | tail -1)
Check:
1. Required fields present
2. Types correct
3. Schema compliance"# Check if port in use
lsof -i :3000
# Check server process
ps aux | grep mcp
# Start with verbose
node server/index.ts --verbose# List available tools
curl http://localhost:3000/mcp/list_tools | jq '.tools[].name'
# Check tool registration
grep "registerTool\|toolRegistry" server/*.ts# Profile tool execution
time curl -X POST http://localhost:3000/mcp/call_tool \
-H "Content-Type: application/json" \
-d '{"name": "slow_tool", "args": {}}'
# Check for blocking operations
grep -i "await\|sync" tools/slow_tool/index.ts# Find malformed JSON
grep -B 5 "JSON\|parse" ~/.claude/debug/mcp-*.log | grep -i error
# Validate JSON
echo '{"test": ...}' | jq '.'# Real-time log monitoring
tail -f ~/.claude/debug/mcp-*.log | grep --line-buffered "tool_use\|result"# Count calls per tool
grep "tool_use" ~/.claude/debug/mcp-*.log | \
grep -oP '"name":"[^"]*"' | \
sort | uniq -c | sort -rn#!/bin/bash
# mcp-health.sh
echo "=== MCP Server Health ==="
# Check server
if curl -s http://localhost:3000/health > /dev/null 2>&1; then
echo "Server: UP"
else
echo "Server: DOWN"
fi
# Recent errors
ERRORS=$(grep -c "error" ~/.claude/debug/mcp-*.log 2>/dev/null || echo 0)
echo "Recent errors: $ERRORS"
# Tool count
TOOLS=$(curl -s http://localhost:3000/mcp/list_tools 2>/dev/null | jq '.tools | length' || echo 0)
echo "Registered tools: $TOOLS"