MCP Dev Inspector

A browser-based inspector for Model Context Protocol (MCP) servers. Connect to any MCP server, browse its tools, execute them with custom arguments, and inspect the JSON-RPC traffic — all from a local web UI.

Built for developers building or debugging MCP servers. Supports OAuth 2.0 authentication and works on Google Cloud Workstations.

Quick Start

Run directly from GitHub using npx — no install required:

npx github:Wave1art/mcp-inspector

This builds (if needed), starts a local server, and opens the inspector in your browser.

Usage

npx github:Wave1art/mcp-inspector [options]

Options

Flag	Default	Description
--mcp-url <url>	—	Full URL of the MCP server to connect to
--port, --mcp-port <n>	6277	MCP server port (shorthand for http://127.0.0.1:<n>)
--inspector-port, -p <n>	6280	Port for the inspector UI
--auth <none|oauth>	none	Authentication mode
-h, --help	—	Show help

Examples

# Connect to an MCP server on the default port (6277)
npx github:Wave1art/mcp-inspector

# Connect to an MCP server at a specific URL
npx github:Wave1art/mcp-inspector --mcp-url http://localhost:8080

# Use a custom inspector port
npx github:Wave1art/mcp-inspector -p 3000

# Connect with OAuth authentication
npx github:Wave1art/mcp-inspector --mcp-url https://my-mcp-server.example.com --auth oauth

Installing as a Dev Dependency

You can also add it to a project so your team can run it via an npm script:

npm install --save-dev github:Wave1art/mcp-inspector

Then add a script to your package.json:

{
  "scripts": {
    "inspect-mcp": "mcp-dev-inspector --mcp-url http://localhost:8080"
  }
}

Run it with:

npm run inspect-mcp

To pull the latest version:

npm install github:Wave1art/mcp-inspector

Features

• Tool browser — lists all tools exposed by the MCP server, grouped by prefix
• Tool executor — fill in arguments via auto-generated forms and call tools directly
• Smart response viewer — renders results as tables, cards, markdown, or raw JSON depending on content
• JSON-RPC log — inspect every request and response between the inspector and the MCP server
• OAuth support — authenticate with MCP servers that require OAuth 2.0 (PKCE + dynamic client registration)
• Dark mode — toggle between light and dark themes
• Collapsible panels — hide the tools list or log panel to focus on what matters
• CLI flags + UI input — set the MCP server address via command-line flags or change it at runtime in the UI

Development

# Install dependencies
npm install

# Start the Angular dev server (hot reload)
npm run dev

# Build for production
npm run build

# Run the production server locally
npm start

# Run tests
npm test

Architecture

• Frontend: Angular 21 with Angular Material, standalone components, signals
• Backend: Express 5 with an HTTP proxy to the target MCP server
• Auth: OAuth 2.0 + PKCE with dynamic client registration
• Transport: JSON-RPC over HTTP, SSE for streaming