📌Overview

Purpose: The MCP Inspector serves as a developer tool designed for testing and debugging Model Context Protocol (MCP) servers.

Overview: This tool facilitates inspections of MCP server implementations without needing to clone the repository. It provides a streamlined way to run a client UI and an MCP proxy server, allowing developers to effectively troubleshoot and optimize their servers.

Key Features:

• Easy Launching: Allows running the inspector via npx without repository cloning, streamlining testing processes for MCP servers.

• Client UI and Proxy Server: Automatically runs a client interface on a default port, along with a proxy server, enhancing usability by offering a visual interface for inspections.

• Environment Configuration: Supports the passing of environment variables and server arguments, providing flexibility in server setup for different testing scenarios.

• Bearer Token Authentication: Enables secure connections to MCP servers via bearer token authentication, ensuring authorized access during inspections.

• Security Measures: Includes necessary security considerations for protecting the proxy server from untrusted networks, emphasizing the importance of secure configurations.

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MCP Inspector

The MCP Inspector is a developer tool for testing and debugging MCP servers.

Running the Inspector

From an MCP Server Repository

To inspect an MCP server implementation, you can use npx. For example, if your server is built at build/index.js:

npx @modelcontextprotocol/inspector node build/index.js

You can pass arguments and environment variables to your MCP server:

# Pass arguments only
npx @modelcontextprotocol/inspector build/index.js arg1 arg2

# Pass environment variables only
npx @modelcontextprotocol/inspector -e KEY=value -e KEY2=$VALUE2 node build/index.js

# Pass both environment variables and arguments
npx @modelcontextprotocol/inspector -e KEY=value -e KEY2=$VALUE2 node build/index.js arg1 arg2

# Use -- to separate inspector flags from server arguments
npx @modelcontextprotocol/inspector -e KEY=$VALUE -- node build/index.js -e server-flag

The inspector runs both a client UI (default port 5173) and an MCP proxy server (default port 3000). You can customize the ports if needed:

CLIENT_PORT=8080 SERVER_PORT=9000 npx @modelcontextprotocol/inspector node build/index.js

For more details on using the inspector, refer to the Inspector section of the MCP docs site and the Debugging guide.

Authentication

The inspector supports bearer token authentication for SSE connections. Enter your token in the UI when connecting to an MCP server.

Security Considerations

The MCP Inspector includes a proxy server that should not be exposed to untrusted networks, as it can spawn local processes and connect to specified MCP servers.

From This Repository

If you're working on the inspector itself:

Development Mode:

npm run dev

Note for Windows users:
Use the following command instead:

npm run dev:windows

Production Mode:

npm run build
npm start

License

This project is licensed under the MIT License—see the LICENSE file for details.