How to integrate Mailerlite MCP with Mastra AI

This guide walks you through connecting Mailerlite to Mastra AI 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 Mastra AI 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 Mastra AI 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 Mastra AI 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.

Also integrate Mailerlite with

OpenAI Agents SDKClaude Agent SDKClaude CodeClaude CoworkCodexOpenClawHermesCLIGoogle ADKLangChainVercel AI SDKLlamaIndexCrewAI

TL;DR

Here's what you'll learn:
  • Set up your environment so Mastra, OpenAI, and Composio work together
  • Create a Tool Router session in Composio that exposes Mailerlite tools
  • Connect Mastra's MCP client to the Composio generated MCP URL
  • Fetch Mailerlite tool definitions and attach them as a toolset
  • Build a Mastra agent that can reason, call tools, and return structured results
  • Run an interactive CLI where you can chat with your Mailerlite agent

What is Mastra AI?

Mastra AI is a TypeScript framework for building AI agents with tool support. It provides a clean API for creating agents that can use external services through MCP.

Key features include:

  • MCP Client: Built-in support for Model Context Protocol servers
  • Toolsets: Organize tools into logical groups
  • Step Callbacks: Monitor and debug agent execution
  • OpenAI Integration: Works with OpenAI models via @ai-sdk/openai

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:
  • Node.js 18 or higher
  • A Composio account with an active API key
  • An OpenAI API key
  • Basic familiarity with TypeScript
2

Getting API Keys for OpenAI and Composio

OpenAI API Key
  • Go to the OpenAI dashboard and create an API key.
  • You need credits or a connected billing setup to use the models.
  • Store the key somewhere safe.
Composio API Key
  • Log in to the Composio dashboard.
  • Go to Settings and copy your API key.
  • This key lets your Mastra agent talk to Composio and reach Mailerlite through MCP.
3

Install dependencies

bash
npm install @composio/core @mastra/core @mastra/mcp @ai-sdk/openai dotenv

Install the required packages.

What's happening:

  • @composio/core is the Composio SDK for creating MCP sessions
  • @mastra/core provides the Agent class
  • @mastra/mcp is Mastra's MCP client
  • @ai-sdk/openai is the model wrapper for OpenAI
  • dotenv loads environment variables from .env
4

Set up environment variables

bash
COMPOSIO_API_KEY=your_composio_api_key_here
COMPOSIO_USER_ID=your_user_id_here
OPENAI_API_KEY=your_openai_api_key_here

Create a .env file in your project root.

What's happening:

  • COMPOSIO_API_KEY authenticates your requests to Composio
  • COMPOSIO_USER_ID tells Composio which user this session belongs to
  • OPENAI_API_KEY lets the Mastra agent call OpenAI models
5

Import libraries and validate environment

typescript
import "dotenv/config";
import { openai } from "@ai-sdk/openai";
import { Agent } from "@mastra/core/agent";
import { MCPClient } from "@mastra/mcp";
import { Composio } from "@composio/core";
import * as readline from "readline";

import type { AiMessageType } from "@mastra/core/agent";

const openaiAPIKey = process.env.OPENAI_API_KEY;
const composioAPIKey = process.env.COMPOSIO_API_KEY;
const composioUserID = process.env.COMPOSIO_USER_ID;

if (!openaiAPIKey) throw new Error("OPENAI_API_KEY is not set");
if (!composioAPIKey) throw new Error("COMPOSIO_API_KEY is not set");
if (!composioUserID) throw new Error("COMPOSIO_USER_ID is not set");

const composio = new Composio({
  apiKey: composioAPIKey as string,
});
What's happening:
  • dotenv/config auto loads your .env so process.env.* is available
  • openai gives you a Mastra compatible model wrapper
  • Agent is the Mastra agent that will call tools and produce answers
  • MCPClient connects Mastra to your Composio MCP server
  • Composio is used to create a Tool Router session
6

Create a Tool Router session for Mailerlite

typescript
async function main() {
  const session = await composio.create(
    composioUserID as string,
    {
      toolkits: ["mailerlite"],
    },
  );

  const composioMCPUrl = session.mcp.url;
  console.log("Mailerlite MCP URL:", composioMCPUrl);
What's happening:
  • create spins up a short-lived MCP HTTP endpoint for this user
  • The toolkits array contains "mailerlite" for Mailerlite access
  • session.mcp.url is the MCP URL that Mastra's MCPClient will connect to
7

Configure Mastra MCP client and fetch tools

typescript
const mcpClient = new MCPClient({
    id: composioUserID as string,
    servers: {
      nasdaq: {
        url: new URL(composioMCPUrl),
        requestInit: {
          headers: session.mcp.headers,
        },
      },
    },
    timeout: 30_000,
  });

console.log("Fetching MCP tools from Composio...");
const composioTools = await mcpClient.getTools();
console.log("Number of tools:", Object.keys(composioTools).length);
What's happening:
  • MCPClient takes an id for this client and a list of MCP servers
  • The headers property includes the x-api-key for authentication
  • getTools fetches the tool definitions exposed by the Mailerlite toolkit
8

Create the Mastra agent

typescript
const agent = new Agent({
    name: "mailerlite-mastra-agent",
    instructions: "You are an AI agent with Mailerlite tools via Composio.",
    model: "openai/gpt-5",
  });
What's happening:
  • Agent is the core Mastra agent
  • name is just an identifier for logging and debugging
  • instructions guide the agent to use tools instead of only answering in natural language
  • model uses openai("gpt-5") to configure the underlying LLM
9

Set up interactive chat interface

typescript
let messages: AiMessageType[] = [];

console.log("Chat started! Type 'exit' or 'quit' to end.\n");

const rl = readline.createInterface({
  input: process.stdin,
  output: process.stdout,
  prompt: "> ",
});

rl.prompt();

rl.on("line", async (userInput: string) => {
  const trimmedInput = userInput.trim();

  if (["exit", "quit", "bye"].includes(trimmedInput.toLowerCase())) {
    console.log("\nGoodbye!");
    rl.close();
    process.exit(0);
  }

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

  messages.push({
    id: crypto.randomUUID(),
    role: "user",
    content: trimmedInput,
  });

  console.log("\nAgent is thinking...\n");

  try {
    const response = await agent.generate(messages, {
      toolsets: {
        mailerlite: composioTools,
      },
      maxSteps: 8,
    });

    const { text } = response;

    if (text && text.trim().length > 0) {
      console.log(`Agent: ${text}\n`);
        messages.push({
          id: crypto.randomUUID(),
          role: "assistant",
          content: text,
        });
      }
    } catch (error) {
      console.error("\nError:", error);
    }

    rl.prompt();
  });

  rl.on("close", async () => {
    console.log("\nSession ended.");
    await mcpClient.disconnect();
    process.exit(0);
  });
}

main().catch((err) => {
  console.error("Fatal error:", err);
  process.exit(1);
});
What's happening:
  • messages keeps the full conversation history in Mastra's expected format
  • agent.generate runs the agent with conversation history and Mailerlite toolsets
  • maxSteps limits how many tool calls the agent can take in a single run
  • onStepFinish is a hook that prints intermediate steps for debugging

Complete Code

Here's the complete code to get you started with Mailerlite and Mastra AI:

typescript
import "dotenv/config";
import { openai } from "@ai-sdk/openai";
import { Agent } from "@mastra/core/agent";
import { MCPClient } from "@mastra/mcp";
import { Composio } from "@composio/core";
import * as readline from "readline";

import type { AiMessageType } from "@mastra/core/agent";

const openaiAPIKey = process.env.OPENAI_API_KEY;
const composioAPIKey = process.env.COMPOSIO_API_KEY;
const composioUserID = process.env.COMPOSIO_USER_ID;

if (!openaiAPIKey) throw new Error("OPENAI_API_KEY is not set");
if (!composioAPIKey) throw new Error("COMPOSIO_API_KEY is not set");
if (!composioUserID) throw new Error("COMPOSIO_USER_ID is not set");

const composio = new Composio({ apiKey: composioAPIKey as string });

async function main() {
  const session = await composio.create(composioUserID as string, {
    toolkits: ["mailerlite"],
  });

  const composioMCPUrl = session.mcp.url;

  const mcpClient = new MCPClient({
    id: composioUserID as string,
    servers: {
      mailerlite: {
        url: new URL(composioMCPUrl),
        requestInit: {
          headers: session.mcp.headers,
        },
      },
    },
    timeout: 30_000,
  });

  const composioTools = await mcpClient.getTools();

  const agent = new Agent({
    name: "mailerlite-mastra-agent",
    instructions: "You are an AI agent with Mailerlite tools via Composio.",
    model: "openai/gpt-5",
  });

  let messages: AiMessageType[] = [];

  const rl = readline.createInterface({
    input: process.stdin,
    output: process.stdout,
    prompt: "> ",
  });

  rl.prompt();

  rl.on("line", async (input: string) => {
    const trimmed = input.trim();
    if (["exit", "quit"].includes(trimmed.toLowerCase())) {
      rl.close();
      return;
    }

    messages.push({ id: crypto.randomUUID(), role: "user", content: trimmed });

    const { text } = await agent.generate(messages, {
      toolsets: { mailerlite: composioTools },
      maxSteps: 8,
    });

    if (text) {
      console.log(`Agent: ${text}\n`);
      messages.push({ id: crypto.randomUUID(), role: "assistant", content: text });
    }

    rl.prompt();
  });

  rl.on("close", async () => {
    await mcpClient.disconnect();
    process.exit(0);
  });
}

main();

Conclusion

You've built a Mastra AI agent that can interact with Mailerlite through Composio's Tool Router. You can extend this further by:
  • Adding other toolkits like Gmail, Slack, or GitHub
  • Building a web-based chat interface around this agent
  • Using multiple MCP endpoints to enable cross-app workflows
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

OpenAI Agents SDK logo

OpenAI Agents SDK

Use Mailerlite MCP with OpenAI Agents SDK

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

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. Mastra AI 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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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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