RETICLE

The Wireshark for the Model Context Protocol (MCP)

See what your agent sees.

Reticle intercepts, visualizes, and profiles MCP JSON-RPC traffic in real time — designed for microsecond-level overhead.

Quick start · Install · Docs · Security · Contributing

What is Reticle?

Reticle is a proxy + UI for debugging MCP integrations:

• inspect raw JSON-RPC messages (requests / notifications / responses)
• correlate request ↔ response instantly
• profile latency and token estimates
• capture server stderr and crashes
• record sessions and export logs

Supported transports: stdio, Streamable HTTP, WebSocket, HTTP/SSE.

Quick start

1) Install

# npm
npm install -g mcp-reticle

# pip
pip install mcp-reticle

# Homebrew
brew install labterminal/mcp-reticle/mcp-reticle

2) Wrap your MCP server (stdio)

Replace your MCP server command with mcp-reticle run --name <name> -- <command...>.

Example (Claude Desktop-style config):

{
  "mcpServers": {
    "filesystem": {
      "command": "mcp-reticle",
      "args": ["run", "--name", "filesystem", "--", "npx", "-y", "@modelcontextprotocol/server-filesystem", "/Users/me/work"]
    }
  }
}

3) Launch the UI

mcp-reticle ui

Optional: log-only mode (no UI)

mcp-reticle run --log -- npx -y @modelcontextprotocol/server-memory

Optional: proxy an HTTP-based MCP server

mcp-reticle proxy --name api --upstream http://localhost:8080 --listen 3001

Installation

If you prefer building from source:

git clone https://github.com/labterminal/mcp-reticle.git
cd mcp-reticle
just build

Documentation

All guides and deep dives are in the GitHub Wiki:

• Getting started
• CLI reference
• Client configuration
• Troubleshooting
• Architecture
• Security & privacy
• Development
• Exports

CLI overview

Full details: CLI reference

Security & privacy

Reticle can capture tool inputs/outputs and server stderr. Treat recordings and exports as sensitive artifacts.

Recommended reading: Security & privacy

Contributing

• Repo guidelines: CONTRIBUTING.md
• Dev setup and commands: Development guide

License

MIT — see LICENSE.