Show HN: I built a better MCP inspector to debug MCP servers

4 months ago 6

Get up and running in seconds with the MCPJam Inspector:

npx @mcpjam/inspector@latest

That's it! The inspector will launch automatically in your browser at http://localhost:6274.

This project is a fork of the @modelcontextprotocol/inspector. Many of the features are the same but with some enhancements. Key features include:

STDIO / SSE / Streamable HTTP - This inspector supports all three protocols. Connect to any MCP server.
Tool Execution - Run server tools with live parameter input. Easily debug errors.
(New) LLM tool interaction - Test your MCP server against a real LLM.
Debugging tools - Enhanced logging experience to debug your server.
Quality of life improvements - Save requests, multi-server connection, saved connections.

Node.js: ^22.7.5 or higher
npm: ^10.0.0 or higher (comes with Node.js)

# Launch inspector with default settings npx @mcpjam/inspector

# Connect to a server built at build/index.js npx @mcpjam/inspector node build/index.js

# Pass custom arguments to your server npx @mcpjam/inspector node server.js --port 3000 --debug

# Load servers from a config file npx @mcpjam/inspector --config ./my-config.json

Example Configuration File

{ "mcpServers": { "my-awesome-server": { "command": "node", "args": ["build/index.js"], "env": { "API_KEY": "your-api-key", "DEBUG": "true" } }, "python-server": { "command": "python", "args": ["-m", "my_mcp_server"], "env": { "PYTHONPATH": "./src" } } } }

The MCPJam Inspector is built as a modern monorepo with three main components:

📦 @mcpjam/inspector ├── 🖥️ client/ # React + TypeScript frontend ├── 🔧 server/ # Express.js backend with WebSocket support └── 🚀 cli/ # Command-line interface

Frontend: React 18, TypeScript, Tailwind CSS, Radix UI
Backend: Express.js, WebSocket (ws), CORS support
CLI: Node.js with shell integration
Build Tools: Vite, TSC, Concurrently

# Clone the repository git clone https://github.com/mcpjam/inspector.git cd inspector # Install dependencies npm install # Start development servers npm run dev

# Build all components npm run build # Test the build npm run start

We put together these commands to help you build locally:

Script Description

npm run dev	Start development servers (client + server)
npm run build	Build all components for production
npm run test	Run test suite
npm run prettier-fix	Format code with Prettier
npm run clean	Clean all build artifacts and reinstall