MCP Inspector#

GraphQL MCP includes a built-in web-based inspector for testing and debugging your MCP tools.

What is the MCP Inspector?#

The MCP Inspector is a GraphiQL-integrated interface that lets you:

• 🔍 Discover Tools - Browse all available MCP tools generated from your schema
• 🧪 Test Tools - Execute tools with custom parameters and see results
• 🔐 Add Authentication - Test with Bearer tokens, API keys, or custom headers
• 📊 Track History - Review previous tool executions
• 📄 View Schemas - Inspect parameter and output schemas for each tool
• ⚡ Real-time Status - Monitor connection status and availability

Enabling the Inspector#

Enable the inspector by setting graphql_http=True when creating your server. Works with any GraphQL library:

from graphql_mcp.server import GraphQLMCP

# With any GraphQL schema (Strawberry, Ariadne, Graphene, etc.)
server = GraphQLMCP(
    schema=your_graphql_schema,
    name="My API",
    graphql_http=True  # This enables both GraphQL and MCP Inspector
)

app = server.http_app()

Example with Strawberry:

import strawberry
from graphql_mcp.server import GraphQLMCP

@strawberry.type
class Query:
    @strawberry.field
    def hello(self, name: str = "World") -> str:
        return f"Hello, {name}!"

schema = strawberry.Schema(query=Query)
server = GraphQLMCP(schema=schema._schema, graphql_http=True)

Accessing the Inspector#

Once your server is running, access the inspector by visiting your GraphQL endpoint in a web browser:

http://localhost:8000/graphql

The inspector interface will automatically appear alongside the GraphiQL interface.

Using the Inspector#

1. Discover Available Tools#

The left panel shows all MCP tools generated from your GraphQL schema:

• Tool names (converted to snake_case)
• Tool descriptions from GraphQL docstrings
• Parameter information

2. Configure Authentication#

If your API requires authentication, use the authentication panel:

Bearer Token: your_token_here

Or add custom headers:

X-API-Key: your_key
Authorization: Bearer token

3. Execute Tools#

1. Select a tool from the list
2. Fill in the parameters (JSON format)
3. Click “Execute”
4. View the results in the output panel

Example parameters:

{
  "name": "Alice",
  "age": 30
}

4. Review Call History#

The inspector maintains a history of your tool calls:

• Timestamp of execution
• Tool name and parameters
• Results or errors
• Response time

Click on any previous call to:

• View the full request/response
• Re-execute with the same parameters
• Copy parameters for modification

5. Inspect Schemas#

Click the schema icon next to any tool to view:

• Input Schema - Required and optional parameters with types
• Output Schema - Expected return type structure
• Documentation - Description from GraphQL schema

Authentication Testing#

The inspector supports various authentication methods:

Bearer Tokens#

Bearer Token: eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9...

API Keys#

Add as custom header:

X-API-Key: your_api_key_here

Custom Headers#

Any additional headers your API requires:

X-Custom-Auth: value
X-Request-ID: 123

Example Workflow#

Here’s a typical testing workflow with the inspector:

1. Start Server with inspector enabled

   server = GraphQLMCP(schema=your_schema, graphql_http=True)
   app = server.http_app()

2. Open Browser to http://localhost:8000/graphql

3. Browse Tools in the inspector panel

4. Add Authentication if required

5. Test a Query Tool

   • Select get_user
   • Parameters: {"id": "123"}
   • Click Execute
   • View results

6. Test a Mutation Tool

   • Select create_user
   • Parameters: {"name": "Alice", "email": "alice@example.com"}
   • Click Execute
   • Verify creation

7. Review History to compare results

8. Export Parameters for use in your application

Inspector vs GraphiQL#

The inspector complements GraphiQL:

You can use both simultaneously to test your API from both perspectives.

Disabling in Production#

For production deployments, disable the GraphQL HTTP endpoint:

server = GraphQLMCP(
    schema=your_schema,
    graphql_http=False  # No GraphiQL or inspector in production
)

This removes both GraphiQL and the MCP Inspector, leaving only the MCP endpoints.

Debugging Tips#

Tool Not Appearing#

• Check that the field is properly defined in your GraphQL schema
• Ensure the field has a description/docstring in the schema
• Verify mutations are enabled (allow_mutations=True)

Authentication Errors#

• Verify token format (include “Bearer " prefix if required)
• Check token hasn’t expired
• Ensure auth configuration matches your API

Type Errors#

• Check parameter types match the schema
• Use proper JSON format for complex types
• Review the schema panel for expected types

Connection Issues#

• Verify server is running
• Check the correct port and path
• Look for CORS errors in browser console

Next Steps#

• Configuration - Configure inspector behavior
• Examples - See inspector in real workflows
• API Reference - Learn about MCP tool APIs