🔌 mcp-probe

🔌 mcp-probe

Probe and inspect any MCP (Model Context Protocol) server from the CLI.

mcp-probe is a zero-dependency MCP client that speaks JSON-RPC 2.0 over stdio. Connect to any MCP server, discover its tools, resources, and prompts, and invoke tools — all from your terminal. Great for debugging servers you're building, auditing third-party servers, or scripting MCP interactions.

Why mcp-probe?

• Debug MCP servers without writing code — one command to discover tools, resources, and prompts. Essential for MCP server developers and security auditors.
• Zero dependencies — pure Python stdlib. Implements the MCP protocol directly. Nothing to install, nothing to trust.
• Works with any MCP server — Node.js (npx), Python, or compiled binaries. Spawn and probe over stdio.
• Pipe-friendly output — human-readable tables for exploration, --json for scripting. Integrates with jq, mcp-guard, and other CLI tools.

Features

• 🔍 Discover — list tools, resources, and prompts exposed by any MCP server
• 🛠️ Invoke — call tools with JSON arguments and pretty-print results
• 🚫 Zero dependencies — pure Python stdlib, implements the MCP protocol directly
• 🎨 Readable output — color-coded, structured terminal display
• 🔧 Any server — works with any stdio MCP server (npx, python, node, …)

Quick Start

pip install mcp-probe

Usage

Pass the server command after --. mcp-probe spawns it as a subprocess and speaks MCP over stdio.

Inspect a server (everything at once)

mcp-probe inspect -- npx -y @modelcontextprotocol/server-everything

● MCP Server
  name:     Everything
  version:  1.0.0
  protocol: 2024-11-05
  caps:     tools, resources, prompts

Tools (1)
  ▸ echo — Echoes back the input
      params: message*:string
...

List only tools

mcp-probe tools -- npx -y @modelcontextprotocol/server-everything

List resources / prompts

mcp-probe resources -- python my_server.py
mcp-probe prompts -- python my_server.py

Invoke a tool

mcp-probe call --tool echo --args '{"message":"hello"}' -- npx -y @modelcontextprotocol/server-everything

✓ Result
hello

How It Works

mcp-probe implements the MCP stdio transport:

1. Spawns your server command as a subprocess
2. Sends the initialize JSON-RPC request and reads the server's capabilities
3. Sends the notifications/initialized acknowledgment
4. Calls tools/list, resources/list, prompts/list, and tools/call as requested
5. Renders results and tears down the subprocess

Messages are newline-delimited JSON (JSON-RPC 2.0). No SDK required.

Development

git clone https://github.com/alvabillwu/mcp-probe.git
cd mcp-probe
pip install -e ".[dev]"
pytest -v

The test suite runs against an in-repo mock MCP server (tests/mock_server.py), so it's fully self-contained.

🔗 Ecosystem

Part of the alvabillwu AI/LLM DevTools suite:

• mcp-guard — Security scanner for MCP server tool manifests
• mcp-compliance-lite — MCP spec conformance tester
• mcpindex — Searchable index and discovery tool for MCP servers
• mcp-factory — MCP server scaffolding CLI

License

MIT © alvabillwu

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