The MCP Inspector is a developer tool designed for testing and debugging Model Context Protocol (MCP) servers. It provides both a graphical user interface (UI) and a command-line interface (CLI) for interacting with MCP server implementations, enabling efficient development and debugging workflows.

How It Works

The inspector operates by running two components: an MCP Inspector Client UI and an MCP Proxy server. The client UI, accessible via a web browser, allows developers to visually test server functionality, explore resources, and manage prompts. The proxy server facilitates communication between the inspector and the MCP server process. This dual-component approach, combined with configurable ports and authentication, offers a flexible environment for MCP server development.

Quick Start & Requirements

• Install/Run: npx @modelcontextprotocol/inspector node build/index.js
• Prerequisites: Node.js version 22.7.5 or higher.
• Details: The inspector runs a client UI on port 6274 and a proxy server on port 6277 by default. These can be customized via environment variables (CLIENT_PORT, SERVER_PORT).
• Docs: MCP docs site, Debugging guide

Highlighted Details

• Supports passing arguments and environment variables to the MCP server.
• Offers bearer token authentication for SSE connections.
• Provides both UI mode for interactive testing and CLI mode for scripting and automation.
• Allows configuration via UI settings or JSON files for multiple server setups.

Maintenance & Community

No specific contributors, sponsorships, or community links were mentioned in the README.

Licensing & Compatibility

• License: MIT License.
• Compatibility: Permissive license suitable for commercial use and integration with closed-source projects.

Limitations & Caveats

The proxy server should not be exposed to untrusted networks due to its ability to spawn local processes and connect to specified MCP servers. Configuration settings can be adjusted in real-time via the UI and persist across sessions.