MITM MCP - Network Traffic Capture & Query System

A JavaScript-based MITM (Man-in-the-Middle) proxy that captures network requests during development and exposes them via Model Context Protocol (MCP) for querying by Claude Code.

What is it?

MITM MCP intercepts HTTP/HTTPS traffic from your browser or application, stores it in SQLite, and lets you query it through Claude Code. Perfect for debugging API calls, tracking errors, and understanding network behavior during development.

Key Features

• Easy setup: No installation needed with npx
• Capture focus: Filter capture to specific domains to keep database small and queries fast
• Error tracking: Find failed requests (4xx/5xx) instantly
• Query with Claude: Ask Claude to find requests, search bodies, filter by method/status
• HTTPS support: Automatic certificate handling
• Zero config: Works out of the box with sensible defaults

Installation

Prerequisites: Node.js 18+

No installation needed! Just use npx:

npx mitmmcp

The proxy starts on port 8080 and stores data in ~/.local/share/mitmmcp/ (or platform equivalent).

Quick Start

1. Start the Proxy

npx mitmmcp

# Optional: custom port or capture filter
npx mitmmcp --port 9090 --capture="*.test,localhost:*"

2. Configure Claude Code MCP Server

claude mcp add --transport stdio mitmmcp -- npx -y -p mitmmcp mitmmcp-server

Then restart Claude Code.

Manual configuration (edit ~/.claude.json)

{
  "mcpServers": {
    "mitmmcp": {
      "type": "stdio",
      "command": "npx",
      "args": ["-y", "-p", "mitmmcp", "mitmmcp-server"]
    }
  }
}

3. Configure Your Browser or Application

For browsers (launches separate Chrome instance with proxy):

# macOS
/Applications/Google\ Chrome.app/Contents/MacOS/Google\ Chrome \
  --user-data-dir="$HOME/.chrome-proxy-profile" \
  --proxy-server="http://localhost:8080"

For applications:

export HTTP_PROXY=http://localhost:8080
export HTTPS_PROXY=http://localhost:8080

4. Query with Claude Code

Ask Claude to analyze captured traffic:

"Start capturing requests for *.myapp.test"
"Show me the most recent failed requests"
"Find all POST requests to /api/users"
"Get errors from third-party APIs triggered by my app at localhost:3000"
"Search for requests containing 'authentication' in the body"

CLI Options

mitmmcp --help

Options:
  -p, --port <port>           Proxy server port (default: 8080)
  -c, --capture <patterns>    Domain patterns to capture (e.g., "*.test,localhost:*")
  -d, --db-path <path>        Custom SQLite database file path
  -h, --help                  Show this help message

Documentation

• Proxy Configuration - PAC files, browser extensions, etc.
• HTTPS Setup - Certificate trust and self-signed upstream servers
• Further Information - Architecture, database schema, MCP tools, etc.

Development

See docs/FURTHER_INFO.md for project structure.

Local Development Setup

git clone https://github.com/cloudshipco/mitmmcp.git
cd mitmmcp
npm install
npm run build
npm run proxy

Development Commands

npm run dev    # Run in development mode
npm run build  # Build
npm test       # Run tests

License

MIT

Contributing

Contributions welcome! Please open an issue or PR.