> ## Documentation Index
> Fetch the complete documentation index at: https://docs.leanmcp.com/llms.txt
> Use this file to discover all available pages before exploring further.

# Debugging MCP Servers

> Learn how to test and debug your MCP servers effectively

# Debugging Your MCP Server

While developing your MCP server, it's essential to ensure it's doing what it's intended to do. This guide covers the best tools and methods for testing and debugging your MCP servers.

## Why Debug Your MCP Server?

Before deploying your MCP server, thorough testing helps you:

* Verify all tools and resources work as expected
* Catch configuration errors early
* Ensure AI agents can properly interact with your server
* Identify performance issues and bottlenecks

## Method 1: MCP Playground (Recommended)

**Best for**: Initial development and comprehensive testing

We've created an open-source platform specifically designed for testing and debugging MCP servers.

### Get Started with MCP Playground

1. **Repository**: [https://github.com/rosaboyle/mcp-playground](https://github.com/rosaboyle/mcp-playground)
2. **Installation**: Clone the repository and follow the setup instructions
3. **Connect**: Add your MCP server URL to the playground
4. **Test**: Interactive interface to test all your MCP tools and resources

### Features

<CardGroup cols={2}>
  <Card title="Interactive Testing" icon="play">
    Test tools and resources with real-time feedback
  </Card>

  <Card title="Request/Response Viewer" icon="eye">
    See exactly what data is being sent and received
  </Card>

  <Card title="Error Detection" icon="exclamation-triangle">
    Detailed error messages and debugging information
  </Card>

  <Card title="Performance Monitoring" icon="chart-line">
    Track response times and identify bottlenecks
  </Card>
</CardGroup>

### How to Use

1. **Install the playground** from the GitHub repository
2. **Start your MCP server** (locally or deployed)
3. **Add your MCP server URL** to the playground
4. **Test individual tools** and verify responses
5. **Check resources** to ensure data is accessible
6. **Debug any issues** using the detailed logs

## Method 2: Postman Testing

**Best for**: API-level testing and automation

Postman provides excellent support for testing MCP servers through its standard HTTP request features.

### Setup Instructions

1. **Open Postman** and create a new collection
2. **Add your MCP server URL** as the base URL
3. **Configure headers** as required by your MCP server
4. **Create requests** for each tool and resource

### Testing Workflow

```json theme={null}
// Example: Testing a tool
POST {{mcp_server_url}}/tools/execute
Content-Type: application/json

{
  "tool_name": "your_tool_name",
  "arguments": {
    "param1": "value1",
    "param2": "value2"
  }
}
```

### Benefits

* **Automated testing** with collection runner
* **Environment variables** for different server instances
* **Test scripts** for validation
* **Easy sharing** with team members

## Method 3: MCP Inspector

**Best for**: Protocol-level debugging and validation

Anthropic provides an official MCP Inspector tool for testing MCP server compliance and functionality.

### About MCP Inspector

The MCP Inspector helps you:

* Validate MCP protocol compliance
* Test server initialization
* Verify tool and resource definitions
* Check error handling

### How to Access

<Note>
  MCP Inspector is available through Anthropic's official tools. Check the [Anthropic documentation](https://docs.anthropic.com/claude/docs/mcp) for the latest access instructions and installation guide.
</Note>

### Usage Instructions

1. **Install** the MCP Inspector following Anthropic's documentation
2. **Configure** your MCP server connection
3. **Run diagnostics** to check protocol compliance
4. **Review results** and fix any identified issues
5. **Re-test** until all checks pass

### What It Checks

* MCP protocol version compatibility
* Tool and resource schema validation
* Error response formatting
* Connection stability
* Performance characteristics

## Method 4: LLM Client Testing

**Best for**: End-to-end user experience testing

<Warning>
  This method is **not recommended** for early debugging. Use it only after your MCP server passes testing with the above methods.
</Warning>

### When to Use This Method

Only test with LLM clients when:

* ✅ Your MCP server passes all playground tests
* ✅ Postman testing shows consistent responses
* ✅ MCP Inspector validates protocol compliance
* ✅ You're ready to test real user scenarios

### Recommended LLM Clients

Test your MCP server with popular AI applications:

<CardGroup cols={3}>
  <Card title="Cursor" icon="cursor">
    AI-powered code editor
  </Card>

  <Card title="Windsurf" icon="wind">
    AI development environment
  </Card>

  <Card title="Claude Desktop" icon="robot">
    Anthropic's official client
  </Card>
</CardGroup>

### Testing Process

1. **Connect** your MCP server to the LLM client
2. **Create test prompts** that should trigger your tools
3. **Monitor behavior** - how does the AI use your tools?
4. **Check responses** - are they what you expected?
5. **Identify confusion points** - where does the AI struggle?

### Example Test Prompts

```text theme={null}
// For a file management MCP
"Please list all files in the current directory and then create a new file called 'test.txt' with the content 'Hello World'"

// For a database MCP  
"Show me all users in the database, then add a new user with name 'John Doe' and email 'john@example.com'"

// For a task management MCP
"Create a new task called 'Review documentation' with priority 'high', then show me all pending tasks"
```

## Best Practices

### Development Workflow

<Steps>
  <Step title="Start with MCP Playground">
    Test basic functionality and fix obvious issues
  </Step>

  <Step title="Use Postman for Edge Cases">
    Test error conditions and boundary cases
  </Step>

  <Step title="Validate with MCP Inspector">
    Ensure protocol compliance
  </Step>

  <Step title="Deploy and Test">
    Test the deployed version before LLM integration
  </Step>

  <Step title="LLM Integration Testing">
    Final validation with real AI clients
  </Step>
</Steps>

### Common Issues and Solutions

<AccordionGroup>
  <Accordion title="Tools not responding">
    **Symptoms**: Tools appear in the client but don't execute

    **Solutions**:

    * Check tool schema definitions
    * Verify parameter validation
    * Review error logs for execution failures
    * Test with MCP Playground first
  </Accordion>

  <Accordion title="Resources not accessible">
    **Symptoms**: AI can't access your data resources

    **Solutions**:

    * Verify resource URIs are correct
    * Check permissions and authentication
    * Test resource endpoints individually
    * Review MCP protocol compliance
  </Accordion>

  <Accordion title="Slow response times">
    **Symptoms**: Long delays between requests and responses

    **Solutions**:

    * Profile your tool execution times
    * Optimize database queries
    * Add caching where appropriate
    * Check network connectivity
  </Accordion>

  <Accordion title="AI misusing tools">
    **Symptoms**: AI calls tools incorrectly or unnecessarily

    **Solutions**:

    * Improve tool descriptions and examples
    * Add better parameter validation
    * Review tool naming conventions
    * Test with clearer prompts
  </Accordion>
</AccordionGroup>

### Debugging Checklist

Before considering your MCP server production-ready:

* [ ] **Basic functionality** tested in MCP Playground
* [ ] **All tools** execute successfully with valid inputs
* [ ] **All resources** return expected data
* [ ] **Error handling** works for invalid inputs
* [ ] **Protocol compliance** validated with MCP Inspector
* [ ] **Performance** meets your requirements
* [ ] **LLM integration** tested with target clients
* [ ] **Documentation** updated with any changes

## Next Steps

<CardGroup cols={2}>
  <Card title="Deploy Your Server" icon="rocket" href="/quickstart#step-4-deploy-your-server">
    Ready to deploy? Follow our deployment guide
  </Card>

  <Card title="Best Practices" icon="star" href="/building/best-practices">
    Learn how to build better MCP servers
  </Card>

  <Card title="GitHub Integration" icon="github" href="/quickstart#alternative-github-integration">
    Set up CI/CD for your MCP server
  </Card>

  <Card title="Get Help" icon="question-circle" href="/support">
    Need assistance? Contact our support team
  </Card>
</CardGroup>

## Additional Resources

* **MCP Playground**: [https://github.com/rosaboyle/mcp-playground](https://github.com/rosaboyle/mcp-playground)
* **Anthropic MCP Documentation**: [https://docs.anthropic.com/claude/docs/mcp](https://docs.anthropic.com/claude/docs/mcp)
* **MCP Protocol Specification**: Official protocol documentation
* **Community Forum**: Share debugging tips and get help from other developers