MCP Integration Guide

Last Updated: 2025-10-25

Guide for integrating external tools using Model Context Protocol (MCP).

What Is MCP?

MCP (Model Context Protocol) is an open protocol that standardizes how applications provide context to LLMs. It allows connecting external tools like Stripe, databases, and custom APIs.

Key Benefits:

✅ Built into Responses API (no separate setup)
✅ Automatic tool discovery
✅ OAuth authentication support
✅ No additional cost (billed as output tokens)

Basic MCP Integration

const response = await openai.responses.create({
  model: 'gpt-5',
  input: 'Roll 2d6 dice',
  tools: [
    {
      type: 'mcp',
      server_label: 'dice',
      server_url: 'https://dmcp.example.com',
    },
  ],
});

Authentication

const response = await openai.responses.create({
  model: 'gpt-5',
  input: 'Create payment link',
  tools: [
    {
      type: 'mcp',
      server_label: 'stripe',
      server_url: 'https://mcp.stripe.com',
      authorization: process.env.STRIPE_OAUTH_TOKEN, // ✅
    },
  ],
});

Important: API does NOT store tokens. Provide with each request.

Popular MCP Servers

Stripe: https://mcp.stripe.com
Database MCP: Custom servers for PostgreSQL, MySQL, MongoDB
Custom APIs: Build your own MCP server

Building Custom MCP Server

MCP server must implement:

1. List Tools Endpoint

// POST /mcp/list_tools
{
  tools: [
    {
      name: 'get_weather',
      description: 'Get weather for a city',
      input_schema: {
        type: 'object',
        properties: {
          city: { type: 'string' },
        },
        required: ['city'],
      },
    },
  ],
}

2. Call Tool Endpoint

// POST /mcp/call_tool
Request: {
  name: 'get_weather',
  arguments: { city: 'San Francisco' }
}

Response: {
  result: {
    temperature: 72,
    condition: 'sunny',
  }
}

Error Handling

try {
  const response = await openai.responses.create({
    model: 'gpt-5',
    input: 'Use tool',
    tools: [{ type: 'mcp', server_url: '...', authorization: '...' }],
  });
} catch (error: any) {
  if (error.type === 'mcp_connection_error') {
    console.error('Server connection failed');
  }
  if (error.type === 'mcp_authentication_error') {
    console.error('Invalid token');
  }
}

Official MCP Docs: https://platform.openai.com/docs/guides/tools-connectors-mcp

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