MCP Inspector

Official interactive tool to test, inspect and validate MCP servers. Visual testing and real-time debugging.

What is the MCP Inspector?

The MCP Inspector is an official tool developed by Anthropic that provides an interactive web interface to test and debug MCP servers. It allows inspecting JSON-RPC messages, testing resources and tools, and validating that your server works correctly before integrating it with real clients.

Visual

Intuitive web interface to interact with your server without writing code.

Real Time

Observe all JSON-RPC messages as they occur, with timestamps and clear formatting.

Complete

Test resources, tools and prompts from a single interface.

Main Features

The Inspector provides all the tools needed to test and validate MCP servers.

Real-Time Inspection

Visualize all JSON-RPC messages exchanged between client and server in real time.

  • Visible Request and Response
  • Timestamps for each message
  • Formatted JSON format
  • Message search and filtering

Resource Testing

List, read and search resources directly from the interface. Validate that your resources work correctly.

  • List all resources
  • Read resource content
  • Search resources by query
  • Validate URIs and metadata

Tool Testing

Execute tools with custom parameters and visualize results immediately.

  • List available tools
  • Execute tools with parameters
  • Validate input schemas
  • View structured results

Prompt Validation

Test prompts with different arguments and validate that they generate expected messages.

  • List available prompts
  • Get prompts with arguments
  • Validate message structure
  • Test different combinations

Installation and Usage

Install the Inspector and start testing your MCP server in minutes.

Installation

Install the Inspector globally or use it as a development dependency

# Global installation
npm install -g @modelcontextprotocol/inspector

# Or as development dependency
npm install -D @modelcontextprotocol/inspector

Basic Usage

Run the Inspector with your MCP server command

# Python server
mcp-inspector --server "python -m my_server"

# TypeScript/Node.js server
mcp-inspector --server "node server.js"

# With additional arguments
mcp-inspector --server "python -m my_server" --args "--config config.json"

Interactive Mode

The Inspector opens an interactive web interface in your browser

# When running, the Inspector:
# 1. Starts the specified MCP server
# 2. Opens a web interface at http://localhost:3000
# 3. Allows visual interaction with the server

# Navigate to the URL shown in the terminal
# Example: http://localhost:3000

Testing and Validation

Common test scenarios to validate that your MCP server works correctly.

Validate Initialization

Verify that the server initializes correctly and reports its capabilities.

Steps:

  1. 1
    Run the Inspector with your server
  2. 2
    Observe the 'initialize' message in the messages tab
  3. 3
    Verify that the response includes correct capabilities
  4. 4
    Confirm that 'initialized' is sent correctly

Expected Result:

The server should report its capabilities (resources, tools, prompts) correctly.

Test Tool List

Validate that all tools are available and have valid schemas.

Steps:

  1. 1
    Navigate to the 'Tools' section in the Inspector
  2. 2
    Click 'List Tools'
  3. 3
    Check that all tools appear
  4. 4
    Verify that each tool has name, description and inputSchema

Expected Result:

All tools should appear with their complete metadata.

Execute a Tool

Test executing a tool with different parameters.

Steps:

  1. 1
    Select a tool from the list
  2. 2
    Complete the form with required parameters
  3. 3
    Click 'Call Tool'
  4. 4
    Review the response in the results panel

Expected Result:

The tool should execute and return a valid result.

Validate Resources

Verify that resources can be listed, read and searched correctly.

Steps:

  1. 1
    Go to the 'Resources' section
  2. 2
    Click 'List Resources'
  3. 3
    Select a resource and click 'Read'
  4. 4
    Test search with different queries

Expected Result:

Resources should be accessible and return valid content.

Inspector Interface

Description of the main sections of the Inspector web interface

Message Panel

Shows all JSON-RPC messages exchanged between client and server. You can see requests, responses and errors with timestamps and formatted JSON.

Resources Section

Allows listing all available resources, reading content from specific resources and searching resources using queries. Validates URIs and metadata.

Tools Section

Lists all available tools and allows executing them with custom parameters. Includes schema validation and result visualization.

Prompts Section

Test prompts with different arguments and validate that they generate expected messages. Useful for validating reusable prompt templates.

Best Practices for Testing

Before Integrating

  • Test all available resources
  • Validate that all tools work
  • Verify input schemas
  • Check error handling
  • Test with invalid parameters

During Development

  • Use the Inspector for iterative development
  • Validate changes immediately
  • Review JSON-RPC messages for debugging
  • Test edge cases and boundary conditions
  • Document expected behaviors

Ready to test your server?

Install the Inspector and start validating your MCP server. Explore more resources and guides.

View on GitHub View Debugging GuideView Tutorials