How to integrate Mailtrap MCP with OpenAI Agents SDK

This guide walks you through connecting Mailtrap to the OpenAI Agents SDK using the Composio tool router. By the end, you'll have a working Mailtrap agent that can send a test email to marketing team, list all emails sent from mailtrap today, create a new inbox for transactional testing through natural language commands. This guide will help you understand how to give your OpenAI Agents SDK agent real control over a Mailtrap account through Composio's Mailtrap MCP server. Before we dive in, let's take a quick look at the key ideas and tools involved.

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Mailtrap is an email delivery platform for safe email testing and transactional email sending. It helps you catch bugs and verify email flows without spamming real inboxes.

49 Tools

Introduction

This guide walks you through connecting Mailtrap to the OpenAI Agents SDK using the Composio tool router. By the end, you'll have a working Mailtrap agent that can send a test email to marketing team, list all emails sent from mailtrap today, create a new inbox for transactional testing through natural language commands.

This guide will help you understand how to give your OpenAI Agents SDK agent real control over a Mailtrap account through Composio's Mailtrap MCP server.

Before we dive in, let's take a quick look at the key ideas and tools involved.

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TL;DR

Here's what you'll learn:
  • Get and set up your OpenAI and Composio API keys
  • Install the necessary dependencies
  • Initialize Composio and create a Tool Router session for Mailtrap
  • Configure an AI agent that can use Mailtrap as a tool
  • Run a live chat session where you can ask the agent to perform Mailtrap operations

What is OpenAI Agents SDK?

The OpenAI Agents SDK is a lightweight framework for building AI agents that can use tools and maintain conversation state. It provides a simple interface for creating agents with hosted MCP tool support.

Key features include:

  • Hosted MCP Tools: Connect to external services through hosted MCP endpoints
  • SQLite Sessions: Persist conversation history across interactions
  • Simple API: Clean interface with Agent, Runner, and tool configuration
  • Streaming Support: Real-time response streaming for interactive applications

What is the Mailtrap MCP server, and what's possible with it?

The Mailtrap MCP server is an implementation of the Model Context Protocol that connects your AI agent and assistants like Claude, Cursor, etc directly to your Mailtrap account. It provides structured and secure access so your agent can perform Mailtrap operations on your behalf.

What is the Composio tool router, and how does it fit here?

What is Composio SDK?

Composio's Composio SDK helps agents find the right tools for a task at runtime. You can plug in multiple toolkits (like Gmail, HubSpot, and GitHub), and the agent will identify the relevant app and action to complete multi-step workflows. This can reduce token usage and improve the reliability of tool calls. Read more here: Getting started with Composio SDK

The tool router generates a secure MCP URL that your agents can access to perform actions.

How the Composio SDK works

The Composio SDK follows a three-phase workflow:

  1. Discovery: Searches for tools matching your task and returns relevant toolkits with their details.
  2. Authentication: Checks for active connections. If missing, creates an auth config and returns a connection URL via Auth Link.
  3. Execution: Executes the action using the authenticated connection.

Step-by-step Guide

Step by step09 STEPS
1

Prerequisites

Before starting, make sure you have:
  • Composio API Key and OpenAI API Key
  • Primary know-how of OpenAI Agents SDK
  • A live Mailtrap project
  • Some knowledge of Python or Typescript
2

Getting API Keys for OpenAI and Composio

OpenAI API Key
  • Go to the OpenAI dashboard and create an API key. You'll need credits to use the models, or you can connect to another model provider.
  • Keep the API key safe.
Composio API Key
3

Install dependencies

npm install @composio/openai-agents @openai/agents dotenv

Install the Composio SDK and the OpenAI Agents SDK.

4

Set up environment variables

bash
OPENAI_API_KEY=sk-...your-api-key
COMPOSIO_API_KEY=your-api-key
USER_ID=composio_user@gmail.com

Create a .env file and add your OpenAI and Composio API keys.

5

Import dependencies

import 'dotenv/config';
import { Composio } from '@composio/core';
import { OpenAIAgentsProvider } from '@composio/openai-agents';
import { Agent, hostedMcpTool, run, OpenAIConversationsSession } from '@openai/agents';
import * as readline from 'readline';
What's happening:
  • You're importing all necessary libraries.
  • The Composio and OpenAIAgentsProvider classes are imported to connect your OpenAI agent to Composio tools like Mailtrap.
6

Set up the Composio instance

dotenv.config();

const composioApiKey = process.env.COMPOSIO_API_KEY;
const userId = process.env.USER_ID;

if (!composioApiKey) {
  throw new Error('COMPOSIO_API_KEY is not set. Create a .env file with COMPOSIO_API_KEY=your_key');
}
if (!userId) {
  throw new Error('USER_ID is not set');
}

// Initialize Composio
const composio = new Composio({
  apiKey: composioApiKey,
  provider: new OpenAIAgentsProvider(),
});
What's happening:
  • dotenv.config() loads your .env file so COMPOSIO_API_KEY and USER_ID are available as environment variables.
  • Creating a Composio instance using the API Key and OpenAIAgentsProvider class.
7

Create a Tool Router session

// Create Tool Router session for Mailtrap
const session = await composio.create(userId as string, {
  toolkits: ['mailtrap'],
});
const mcpUrl = session.mcp.url;

What is happening:

  • You give the Tool Router the user id and the toolkits you want available. Here, it is only mailtrap.
  • The router checks the user's Mailtrap connection and prepares the MCP endpoint.
  • The returned session.mcp.url is the MCP URL that your agent will use to access Mailtrap.
  • This approach keeps things lightweight and lets the agent request Mailtrap tools only when needed during the conversation.
8

Configure the agent

// Configure agent with MCP tool
const agent = new Agent({
  name: 'Assistant',
  model: 'gpt-5',
  instructions:
    'You are a helpful assistant that can access Mailtrap. Help users perform Mailtrap operations through natural language.',
  tools: [
    hostedMcpTool({
      serverLabel: 'tool_router',
      serverUrl: mcpUrl,
      headers: { 'x-api-key': composioApiKey },
      requireApproval: 'never',
    }),
  ],
});
What's happening:
  • We're creating an Agent instance with a name, model (gpt-5), and clear instructions about its purpose.
  • The agent's instructions tell it that it can access Mailtrap and help with queries, inserts, updates, authentication, and fetching database information.
  • The tools array includes a hostedMcpTool that connects to the MCP server URL we created earlier.
  • The headers object includes the Composio API key for secure authentication with the MCP server.
  • requireApproval: 'never' means the agent can execute Mailtrap operations without asking for permission each time, making interactions smoother.
9

Start chat loop and handle conversation

// Keep conversation state across turns
const conversationSession = new OpenAIConversationsSession();

// Simple CLI
const rl = readline.createInterface({
  input: process.stdin,
  output: process.stdout,
  prompt: 'You: ',
});

console.log('\nComposio Tool Router session created.');
console.log('\nChat started. Type your requests below.');
console.log("Commands: 'exit', 'quit', or 'q' to end\n");

try {
  const first = await run(agent, 'What can you help me with?', { session: conversationSession });
  console.log(`Assistant: ${first.finalOutput}\n`);
} catch (e) {
  console.error('Error:', e instanceof Error ? e.message : e, '\n');
}

rl.prompt();

rl.on('line', async (userInput) => {
  const text = userInput.trim();

  if (['exit', 'quit', 'q'].includes(text.toLowerCase())) {
    console.log('Goodbye!');
    rl.close();
    process.exit(0);
  }

  if (!text) {
    rl.prompt();
    return;
  }

  try {
    const result = await run(agent, text, { session: conversationSession });
    console.log(`\nAssistant: ${result.finalOutput}\n`);
  } catch (e) {
    console.error('Error:', e instanceof Error ? e.message : e, '\n');
  }

  rl.prompt();
});

rl.on('close', () => {
  console.log('\n👋 Session ended.');
  process.exit(0);
});
What's happening:
  • The program prints a session URL that you visit to authorize Mailtrap.
  • After authorization, the chat begins.
  • Each message you type is processed by the agent using run().
  • The responses are printed to the console.
  • Typing exit, quit, or q cleanly ends the chat.

Complete Code

Here's the complete code to get you started with Mailtrap and OpenAI Agents SDK:

import 'dotenv/config';
import { Composio } from '@composio/core';
import { OpenAIAgentsProvider } from '@composio/openai-agents';
import { Agent, hostedMcpTool, run, OpenAIConversationsSession } from '@openai/agents';
import * as readline from 'readline';

const composioApiKey = process.env.COMPOSIO_API_KEY;
const userId = process.env.USER_ID;

if (!composioApiKey) {
  throw new Error('COMPOSIO_API_KEY is not set. Create a .env file with COMPOSIO_API_KEY=your_key');
}
if (!userId) {
  throw new Error('USER_ID is not set');
}

// Initialize Composio
const composio = new Composio({
  apiKey: composioApiKey,
  provider: new OpenAIAgentsProvider(),
});

async function main() {
  // Create Tool Router session
  const session = await composio.create(userId as string, {
    toolkits: ['mailtrap'],
  });
  const mcpUrl = session.mcp.url;

  // Configure agent with MCP tool
  const agent = new Agent({
    name: 'Assistant',
    model: 'gpt-5',
    instructions:
      'You are a helpful assistant that can access Mailtrap. Help users perform Mailtrap operations through natural language.',
    tools: [
      hostedMcpTool({
        serverLabel: 'tool_router',
        serverUrl: mcpUrl,
        headers: { 'x-api-key': composioApiKey },
        requireApproval: 'never',
      }),
    ],
  });

  // Keep conversation state across turns
  const conversationSession = new OpenAIConversationsSession();

  // Simple CLI
  const rl = readline.createInterface({
    input: process.stdin,
    output: process.stdout,
    prompt: 'You: ',
  });

  console.log('\nComposio Tool Router session created.');
  console.log('\nChat started. Type your requests below.');
  console.log("Commands: 'exit', 'quit', or 'q' to end\n");

  try {
    const first = await run(agent, 'What can you help me with?', { session: conversationSession });
    console.log(`Assistant: ${first.finalOutput}\n`);
  } catch (e) {
    console.error('Error:', e instanceof Error ? e.message : e, '\n');
  }

  rl.prompt();

  rl.on('line', async (userInput) => {
    const text = userInput.trim();

    if (['exit', 'quit', 'q'].includes(text.toLowerCase())) {
      console.log('Goodbye!');
      rl.close();
      process.exit(0);
    }

    if (!text) {
      rl.prompt();
      return;
    }

    try {
      const result = await run(agent, text, { session: conversationSession });
      console.log(`\nAssistant: ${result.finalOutput}\n`);
    } catch (e) {
      console.error('Error:', e instanceof Error ? e.message : e, '\n');
    }

    rl.prompt();
  });

  rl.on('close', () => {
    console.log('\nSession ended.');
    process.exit(0);
  });
}

main().catch((err) => {
  console.error('Fatal error:', err);
  process.exit(1);
});

Conclusion

This was a starter code for integrating Mailtrap MCP with OpenAI Agents SDK to build a functional AI agent that can interact with Mailtrap.

Key features:

  • Hosted MCP tool integration through Composio's Tool Router
  • SQLite session persistence for conversation history
  • Simple async chat loop for interactive testing
You can extend this by adding more toolkits, implementing custom business logic, or building a web interface around the agent.
TOOLS

Supported Tools

Every Mailtrap action and event your agent gets out of the box.

Clean Inbox

Tool to clean an inbox in Mailtrap by deleting all messages.

Create Contact

Tool to create a new contact in Mailtrap.

Create Contact Event

Tool to create a contact event in Mailtrap.

Create Contact Export

Tool to create a contact export job for a Mailtrap account.

Create Contact Field

Tool to create a custom contact field in Mailtrap.

Create Contact List

Tool to create a new contact list in Mailtrap.

Create Email Template

Tool to create a new email template in Mailtrap account.

Create Sending Domain

Tool to create a new sending domain in Mailtrap.

Delete Contact

Tool to delete a contact from a Mailtrap account.

Delete Contact Field

Tool to delete a contact field by its ID.

Delete Contact List

Tool to delete a contact list by its ID.

Delete Email Template

Tool to delete an email template from a Mailtrap account.

Delete Project

Tool to delete a project from Mailtrap.

Delete Sending Domain

Tool to delete a sending domain from a Mailtrap account.

Get Billing Usage

Tool to retrieve current billing cycle usage for an account.

Get Contact

Tool to retrieve a contact by UUID or email address from Mailtrap.

Get Contact Export

Tool to retrieve the status of a contact export.

Get Contact Field

Tool to retrieve contact field details by field ID.

Get Contact Import Status

Tool to retrieve the status of a contact import operation.

Get Contact List

Tool to retrieve a specific contact list by its ID.

Get Email Template

Tool to retrieve details of a specific email template by ID.

Get Inbox Attributes

Tool to retrieve inbox attributes from Mailtrap.

Get Message HTML Body

Tool to retrieve the HTML body of a message from Mailtrap.

Get Permission Resources

Tool to retrieve all resources in account for permission management.

Get Project by ID

Tool to retrieve project details from Mailtrap by project ID.

Get Sending Domain

Tool to retrieve sending domain details from Mailtrap.

Get Sending Stats

Tool to retrieve email sending statistics from Mailtrap for a specific account.

Get Sending Stats by Categories

Tool to retrieve email sending statistics grouped by categories.

Get Sending Stats by Date

Tool to retrieve email sending statistics aggregated by date.

Get Sending Stats by Domains

Tool to retrieve sending statistics grouped by domains for a Mailtrap account.

Get Sending Stats by ESP

Tool to retrieve email sending statistics grouped by email service providers (ESPs) for a specified date range.

Import Contacts

Tool to import contacts in bulk to Mailtrap.

List Accounts

Tool to list all Mailtrap accounts you have access to.

List Contact Fields

Tool to get all contact fields for a Mailtrap account.

List Contact Lists

Tool to retrieve all contact lists for a Mailtrap account.

List Email Templates

Tool to retrieve all email templates for a Mailtrap account.

List Inboxes

Tool to get a list of inboxes for a Mailtrap account.

List Messages in Inbox

Tool to get messages from a Mailtrap inbox.

List Projects

Tool to get a list of projects for a Mailtrap account.

List Sending Domains

Tool to list all sending domains for a Mailtrap account.

List Email Suppressions

Tool to list suppressed email addresses for a Mailtrap account.

Mark Inbox as Read

Tool to mark all messages in a Mailtrap inbox as read.

Reset Inbox Credentials

Tool to reset SMTP credentials for a Mailtrap inbox.

Update contact

Tool to update an existing contact in Mailtrap.

Update Contact Field

Tool to update a contact field in Mailtrap.

Update Contact List

Tool to update a contact list's name in Mailtrap.

Update Email Template

Tool to update an existing email template in Mailtrap account.

Update inbox

Tool to update an inbox's settings in Mailtrap.

Update project

Tool to update a project's name in Mailtrap.

FAQ

Frequently asked questions

With a standalone Mailtrap MCP server, the agents and LLMs can only access a fixed set of Mailtrap tools tied to that server. However, with the Composio Tool Router, agents can dynamically load tools from Mailtrap and many other apps based on the task at hand, all through a single MCP endpoint.

Yes, you can. OpenAI Agents SDK fully supports MCP integration. You get structured tool calling, message history handling, and model orchestration while Tool Router takes care of discovering and serving the right Mailtrap tools.

Yes, absolutely. You can configure which Mailtrap scopes and actions are allowed when connecting your account to Composio. You can also bring your own OAuth credentials or API configuration so you keep full control over what the agent can do.

All sensitive data such as tokens, keys, and configuration is fully encrypted at rest and in transit. Composio is SOC 2 Type 2 compliant and follows strict security practices so your Mailtrap data and credentials are handled as safely as possible.

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