How to integrate Mailerlite MCP with OpenAI Agents SDK

This guide walks you through connecting Mailerlite to the OpenAI Agents SDK using the Composio tool router. By the end, you'll have a working Mailerlite agent that can create a new subscriber group called vip customers, add a custom field for subscriber birthday, create a segment for recent e-commerce buyers through natural language commands. This guide will help you understand how to give your OpenAI Agents SDK agent real control over a Mailerlite account through Composio's Mailerlite MCP server. Before we dive in, let's take a quick look at the key ideas and tools involved.

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MailerLite is an email marketing service for building, sending, and automating campaigns. It helps businesses reach audiences with beautiful emails, landing pages, and advanced automation.

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Introduction

This guide walks you through connecting Mailerlite to the OpenAI Agents SDK using the Composio tool router. By the end, you'll have a working Mailerlite agent that can create a new subscriber group called vip customers, add a custom field for subscriber birthday, create a segment for recent e-commerce buyers through natural language commands.

This guide will help you understand how to give your OpenAI Agents SDK agent real control over a Mailerlite account through Composio's Mailerlite 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 Mailerlite
  • Configure an AI agent that can use Mailerlite as a tool
  • Run a live chat session where you can ask the agent to perform Mailerlite 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 Mailerlite MCP server, and what's possible with it?

The Mailerlite MCP server is an implementation of the Model Context Protocol that connects your AI agent and assistants like Claude, Cursor, etc directly to your Mailerlite account. It provides structured and secure access to your email marketing tools, so your agent can create campaigns, manage subscribers, automate workflows, and oversee your shop integrations with ease.

  • Campaign automation and workflow management: Instruct your agent to create or delete automations, streamlining your email marketing processes and ensuring timely communication with your audience.
  • E-commerce customer and shop integration: Let your agent create, update, or remove e-commerce customers and shops for seamless sales tracking, customer onboarding, or data syncing.
  • Subscriber group and segment organization: Have your agent create custom fields, new subscriber groups, or targeted segments so you can send highly personalized campaigns.
  • Webhook registration for real-time updates: Direct your agent to set up webhooks for specific events, enabling instant notifications and integrations with other systems as actions happen in Mailerlite.
  • Efficient cleanup and management: Ask your agent to delete outdated automations, customers, or shops, helping you keep your Mailerlite workspace organized and up to date.

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 Mailerlite 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 Mailerlite.
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 Mailerlite
const session = await composio.create(userId as string, {
  toolkits: ['mailerlite'],
});
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 mailerlite.
  • The router checks the user's Mailerlite connection and prepares the MCP endpoint.
  • The returned session.mcp.url is the MCP URL that your agent will use to access Mailerlite.
  • This approach keeps things lightweight and lets the agent request Mailerlite 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 Mailerlite. Help users perform Mailerlite 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 Mailerlite 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 Mailerlite 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 Mailerlite.
  • 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 Mailerlite 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: ['mailerlite'],
  });
  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 Mailerlite. Help users perform Mailerlite 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 Mailerlite MCP with OpenAI Agents SDK to build a functional AI agent that can interact with Mailerlite.

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 Mailerlite action and event your agent gets out of the box.

Add Product to Category

Tool to add a product to a category in an e-commerce shop.

Add Subscriber To Group

Tool to assign an existing subscriber to a group.

Create automation

Create automation

Create Campaign

Tool to create a new email campaign (draft) with specified type, content, and targeting.

Create E-commerce Cart Item

Tool to add an item to a shopping cart.

Create E-commerce Category

Tool to create a new product category for a shop.

Create/Update E-commerce Customer

Tool to create or update a customer record for a shop.

Create E-commerce Order

Tool to create a new order for a shop.

Create E-commerce Product

Tool to create a new product for an e-commerce shop.

Create E-commerce Shop

Tool to connect a new e-commerce shop.

Create Field

Tool to create a new custom field.

Create Group

Tool to create a new subscriber group.

Create Segment

Tool to create a new subscriber segment.

Create Subscriber

Tool to create or update (upsert) a subscriber by email.

Create Webhook

Tool to register a new webhook URL for specified event types.

Delete Automation

Tool to delete an automation workflow by ID.

Delete E-commerce Cart Item

Tool to remove an item from a cart in an e-commerce shop.

Delete E-commerce Category

Tool to delete a product category from an e-commerce shop by IDs.

Delete E-commerce Customer

Tool to delete a customer from an e-commerce shop by IDs.

Delete E-commerce Order

Tool to delete an order from a shop.

Delete E-commerce Product

Tool to delete a product from an e-commerce shop by IDs.

Delete E-commerce Shop

Tool to disconnect an e-commerce shop by ID.

Delete Field

Tool to delete a custom field.

Delete Group

Tool to delete a subscriber group by ID.

Delete Segment

Tool to delete a segment by ID.

Delete Subscriber

Tool to delete a subscriber by ID.

Delete Webhook

Tool to remove a webhook subscription by ID.

Execute Batch Request

Tool to execute multiple API requests in a single batch call (max 50 requests).

Forget Subscriber

Tool to forget a subscriber completely (GDPR compliant deletion).

Get Account Info

Tool to retrieve basic MailerLite account details.

Get Account Stats

Tool to retrieve usage statistics and performance metrics for the account.

Get Automation

Tool to retrieve details of a specific automation by ID.

Get Automation Activity

Tool to retrieve subscriber activity for a specific automation.

Get Campaign Languages

Tool to retrieve a list of all available campaign languages.

Get Campaigns

Tool to retrieve a list of all campaigns.

Get E-commerce Cart

Tool to fetch details of a specific cart by shop ID and cart ID.

Get E-commerce Cart Item

Tool to fetch details of a specific cart item by shop ID, cart ID, and item ID.

Get E-commerce Category

Tool to fetch details of a specific product category by shop and category ID.

Get E-commerce Customer

Tool to fetch details of a customer by shop and customer ID.

Get E-commerce Customers

Tool to list customers for a specific shop.

Get E-commerce Order

Tool to fetch details of a specific e-commerce order by shop ID and order ID.

Get E-commerce Product

Tool to fetch details of a specific e-commerce product by shop and product ID.

Get E-commerce Shop

Tool to fetch details of a specific e-commerce shop by ID.

Get E-commerce Shops

Tool to list all e-commerce shops connected to the account.

Get Fields

Tool to retrieve all custom fields defined in the account.

Get Group

Tool to retrieve details of a specific subscriber group by ID.

Get Groups

Tool to retrieve all subscriber groups.

Get Group Subscribers

Tool to list subscribers within a group by ID.

Get Import Status

Tool to retrieve the status and detailed report of a subscriber import operation by import ID.

Get Segment

Tool to retrieve a specific segment by ID.

Get Segments

Tool to retrieve all segments in the account.

Get Segment Subscribers

Tool to retrieve all subscribers belonging to a specific segment.

Get Subscriber

Tool to fetch a single subscriber by ID or email address.

Get Subscriber Activity

Tool to fetch the activity log for a specific subscriber.

Get Subscribers

Tool to retrieve all subscribers.

Get Subscribers Stats

Tool to get subscriber statistics for the account.

Get Webhook

Tool to retrieve details of a specific webhook by ID.

Get Webhooks

Tool to retrieve all configured webhooks.

Import E-commerce Categories

Tool to bulk import categories to an e-commerce shop.

Import E-commerce Orders

Tool to bulk import orders to an e-commerce shop.

Import E-commerce Products

Tool to bulk import products to an e-commerce shop.

Import Subscribers to Group

Tool to bulk import multiple subscribers to a specific group.

List Automations

Tool to retrieve all automations in your MailerLite account.

List E-commerce Cart Items

Tool to list all items in a specific cart for an e-commerce shop.

List E-commerce Carts

Tool to list all carts for a specific shop.

List E-commerce Categories

Tool to list all product categories for a shop.

List E-commerce Category Products

Tool to list all products in a specific e-commerce category.

List E-commerce Orders

Tool to list all orders for a specific e-commerce shop.

List E-commerce Products

Tool to list all products for a specific e-commerce shop.

List Forms

Tool to retrieve all forms of a specific type (popup, embedded, or promotion).

List Timezones

Tool to retrieve all available timezones supported by MailerLite.

Remove Product From Category

Tool to remove a product from a category in an e-commerce shop.

Remove Subscriber From Group

Tool to remove a subscriber from a group by ID.

Set Double Opt-In

Tool to enable or disable double opt-in for new subscribers.

Update E-commerce Cart

Tool to update an existing cart's checkout URL or total price.

Update E-commerce Cart Item

Tool to update a cart item's quantity or properties in an e-commerce cart.

Update E-commerce Category

Tool to update an existing product category in an e-commerce shop.

Update E-commerce Customer

Tool to update a customer's data for a shop by IDs.

Update E-commerce Order

Tool to update an existing order's status or total price in an e-commerce shop.

Update E-commerce Product

Tool to update an existing product in an e-commerce shop by IDs.

Update E-commerce Shop

Tool to update settings of a connected e-commerce shop by ID.

Update Field

Tool to update the title of an existing custom field.

Update Group

Tool to update a group's name by ID.

Update Segment

Tool to rename an existing segment by ID.

Update Subscriber

Tool to update an existing subscriber's information by ID.

Update Webhook

Tool to update an existing MailerLite webhook.

FRAMEWORKS

How to build Mailerlite MCP Agent with another framework

Claude Agent SDK logo

Claude Agent SDK

Use Mailerlite MCP with Claude Agent SDK

Claude Code logo

Claude Code

Use Mailerlite MCP with Claude Code

Claude Cowork logo

Claude Cowork

Use Mailerlite MCP with Claude Cowork

Codex logo

Codex

Use Mailerlite MCP with Codex

OpenClaw logo

OpenClaw

Use Mailerlite MCP with OpenClaw

Hermes logo

Hermes

Use Mailerlite MCP with Hermes

CLI logo

CLI

Use Mailerlite MCP with CLI

Google ADK logo

Google ADK

Use Mailerlite MCP with Google ADK

LangChain logo

LangChain

Use Mailerlite MCP with LangChain

Vercel AI SDK logo

Vercel AI SDK

Use Mailerlite MCP with Vercel AI SDK

Mastra AI logo

Mastra AI

Use Mailerlite MCP with Mastra AI

LlamaIndex logo

LlamaIndex

Use Mailerlite MCP with LlamaIndex

CrewAI logo

CrewAI

Use Mailerlite MCP with CrewAI

FAQ

Frequently asked questions

With a standalone Mailerlite MCP server, the agents and LLMs can only access a fixed set of Mailerlite tools tied to that server. However, with the Composio Tool Router, agents can dynamically load tools from Mailerlite 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 Mailerlite tools.

Yes, absolutely. You can configure which Mailerlite 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 Mailerlite data and credentials are handled as safely as possible.

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Co-founder, Slashy

A lot of students tell us that the moment their connected tools start talking to each other inside Opennote feels almost magical. The agent just knows them, and it's immensely helped keep new users on the platform.

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Abhi Arya
Co-founder, Opennote

We chose Composio over Pipedream because it delivered depth where it mattered — niche tools and tricky edge cases other platforms simply ignored. That gave us confidence to scale without compromising.

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CEO, Zams

As a solo builder, shipping fast is life or death. The only way I can outcompete incumbents is by outmanoeuvring them. Getting bogged down managing agent auth would have been a death sentence.

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Founder, Extra Thursday

Before Composio, adding tool integrations was slow and resource-intensive. Each one could take weeks of engineering time, and maintaining them meant constantly keeping up with API changes.

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Founder & CEO, SwarmZero

With hands-on help from their founder, we integrated Gmail and Google Drive in just 30 minutes. This level of personal support and commitment is exactly what startups should strive for.

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Co-Founder, Ingram Technologies