# How to integrate Mailerlite MCP with Vercel AI SDK v6

```json
{
  "title": "How to integrate Mailerlite MCP with Vercel AI SDK v6",
  "toolkit": "Mailerlite",
  "toolkit_slug": "mailerlite",
  "framework": "Vercel AI SDK",
  "framework_slug": "ai-sdk",
  "url": "https://composio.dev/toolkits/mailerlite/framework/ai-sdk",
  "markdown_url": "https://composio.dev/toolkits/mailerlite/framework/ai-sdk.md",
  "updated_at": "2026-05-12T10:18:17.531Z"
}
```

## Introduction

This guide walks you through connecting Mailerlite to Vercel AI SDK v6 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 Vercel AI 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.

## Also integrate Mailerlite with

- [OpenAI Agents SDK](https://composio.dev/toolkits/mailerlite/framework/open-ai-agents-sdk)
- [Claude Agent SDK](https://composio.dev/toolkits/mailerlite/framework/claude-agents-sdk)
- [Claude Code](https://composio.dev/toolkits/mailerlite/framework/claude-code)
- [Claude Cowork](https://composio.dev/toolkits/mailerlite/framework/claude-cowork)
- [Codex](https://composio.dev/toolkits/mailerlite/framework/codex)
- [OpenClaw](https://composio.dev/toolkits/mailerlite/framework/openclaw)
- [Hermes](https://composio.dev/toolkits/mailerlite/framework/hermes-agent)
- [CLI](https://composio.dev/toolkits/mailerlite/framework/cli)
- [Google ADK](https://composio.dev/toolkits/mailerlite/framework/google-adk)
- [LangChain](https://composio.dev/toolkits/mailerlite/framework/langchain)
- [Mastra AI](https://composio.dev/toolkits/mailerlite/framework/mastra-ai)
- [LlamaIndex](https://composio.dev/toolkits/mailerlite/framework/llama-index)
- [CrewAI](https://composio.dev/toolkits/mailerlite/framework/crew-ai)

## TL;DR

Here's what you'll learn:
- How to set up and configure a Vercel AI SDK agent with Mailerlite integration
- Using Composio's Tool Router to dynamically load and access Mailerlite tools
- Creating an MCP client connection using HTTP transport
- Building an interactive CLI chat interface with conversation history management
- Handling tool calls and results within the Vercel AI SDK framework

## What is Vercel AI SDK?

The Vercel AI SDK is a TypeScript library for building AI-powered applications. It provides tools for creating agents that can use external services and maintain conversation state.
Key features include:
- streamText: Core function for streaming responses with real-time tool support
- MCP Client: Built-in support for Model Context Protocol via @ai-sdk/mcp
- Step Counting: Control multi-step tool execution with stopWhen: stepCountIs()
- OpenAI Provider: Native integration with OpenAI models

## 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.

## Supported Tools

| Tool slug | Name | Description |
|---|---|---|
| `MAILERLITE_ADD_PRODUCT_TO_CATEGORY` | Add Product to Category | Tool to add a product to a category in an e-commerce shop. Use when you need to assign or link a product to a specific category for organization and marketing purposes. |
| `MAILERLITE_ADD_SUBSCRIBER_TO_GROUP` | Add Subscriber To Group | Tool to assign an existing subscriber to a group. Use when you need to add a subscriber to a specific group in your MailerLite account. |
| `MAILERLITE_CREATE_AUTOMATION` | Create automation | Create automation |
| `MAILERLITE_CREATE_CAMPAIGN` | Create Campaign | Tool to create a new email campaign (draft) with specified type, content, and targeting. Use when you need to create a campaign programmatically with email settings and optional audience targeting via groups or segments. HTML content support is also plan-dependent; insufficient plan capabilities result in `can_be_scheduled=false` on the created draft. |
| `MAILERLITE_CREATE_ECOMMERCE_CART_ITEM` | Create E-commerce Cart Item | Tool to add an item to a shopping cart. Creates the cart if it does not exist. Use for abandoned cart automation. |
| `MAILERLITE_CREATE_ECOMMERCE_CATEGORY` | Create E-commerce Category | Tool to create a new product category for a shop. Use when organizing products into categories or setting up shop taxonomy with automation preferences. |
| `MAILERLITE_CREATE_ECOMMERCE_CUSTOMER` | Create/Update E-commerce Customer | Tool to create or update a customer record for a shop. Use when syncing shop customers or onboarding new purchases. |
| `MAILERLITE_CREATE_ECOMMERCE_ORDER` | Create E-commerce Order | Tool to create a new order for a shop. Use when recording customer purchases or syncing order data from external systems. |
| `MAILERLITE_CREATE_ECOMMERCE_PRODUCT` | Create E-commerce Product | Tool to create a new product for an e-commerce shop. Use when adding products to a shop for tracking sales, automations, and customer interactions. |
| `MAILERLITE_CREATE_ECOMMERCE_SHOP` | Create E-commerce Shop | Tool to connect a new e-commerce shop. Use when you need to integrate a store for automations, product imports, and sales tracking. |
| `MAILERLITE_CREATE_FIELD` | Create Field | Tool to create a new custom field. Use when distinct subscriber attributes are needed before assigning or updating subscriber data. Call once per field key. |
| `MAILERLITE_CREATE_GROUP` | Create Group | Tool to create a new subscriber group. Use after deciding the group name for categorization. Store `group_id` from the response — required by MAILERLITE_UPDATE_GROUP, MAILERLITE_DELETE_GROUP, and MAILERLITE_GET_GROUP_SUBSCRIBERS. |
| `MAILERLITE_CREATE_SEGMENT` | Create Segment | Tool to create a new subscriber segment. Use when grouping subscribers by custom criteria before sending targeted campaigns. |
| `MAILERLITE_CREATE_SUBSCRIBER` | Create Subscriber | Tool to create or update (upsert) a subscriber by email. Use when adding new subscribers or updating existing ones without needing their ID. If subscriber exists, updates non-destructively (omitted fields/groups are preserved). |
| `MAILERLITE_CREATE_WEBHOOK` | Create Webhook | Tool to register a new webhook URL for specified event types. Use when you need real-time notifications for selected MailerLite events. |
| `MAILERLITE_DELETE_AUTOMATION` | Delete Automation | Tool to delete an automation workflow by ID. Deletion is permanent and irreversible — always require explicit user confirmation before calling. Use when you need to remove an automation after confirming it's no longer needed. Returns success=True on 204 No Content. |
| `MAILERLITE_DELETE_ECOMMERCE_CART_ITEM` | Delete E-commerce Cart Item | Tool to remove an item from a cart in an e-commerce shop. Use when you need to delete a specific product from a customer's shopping cart. |
| `MAILERLITE_DELETE_ECOMMERCE_CATEGORY` | Delete E-commerce Category | Tool to delete a product category from an e-commerce shop by IDs. Use when you need to remove a specific category from your MailerLite store. |
| `MAILERLITE_DELETE_ECOMMERCE_CUSTOMER` | Delete E-commerce Customer | Tool to delete a customer from an e-commerce shop by IDs. Use when you need to remove a specific customer from your MailerLite store. |
| `MAILERLITE_DELETE_ECOMMERCE_ORDER` | Delete E-commerce Order | Tool to delete an order from a shop. Use when you need to remove an order and its associated cart from MailerLite. Returns the deleted order details on success. |
| `MAILERLITE_DELETE_ECOMMERCE_PRODUCT` | Delete E-commerce Product | Tool to delete a product from an e-commerce shop by IDs. Use when you need to remove a specific product from your MailerLite store. |
| `MAILERLITE_DELETE_ECOMMERCE_SHOP` | Delete E-commerce Shop | Tool to disconnect an e-commerce shop by ID. Use when you have the shop's unique identifier and want to remove it from your MailerLite account. |
| `MAILERLITE_DELETE_FIELD` | Delete Field | Tool to delete a custom field. Use when a field is obsolete and you need to remove it from your MailerLite account. Returns success=True on 204 No Content. |
| `MAILERLITE_DELETE_GROUP` | Delete Group | Tool to delete a subscriber group by ID. Permanently removes the group and all its subscriber associations — irreversible with no undo. Use when you need to remove an existing subscriber group from your MailerLite account. Require explicit user confirmation before invoking. Returns success=True on 204 No Content. |
| `MAILERLITE_DELETE_SEGMENT` | Delete Segment | Tool to delete a segment by ID. Use when you need to remove an existing segment from your MailerLite account. Returns success=True on 204 No Content. |
| `MAILERLITE_DELETE_SUBSCRIBER` | Delete Subscriber | Tool to delete a subscriber by ID. Use when you have the subscriber ID and want to remove them from your MailerLite account. Returns success=True on 204 No Content. |
| `MAILERLITE_DELETE_WEBHOOK` | Delete Webhook | Tool to remove a webhook subscription by ID. Use when you need to delete a webhook after confirming it is no longer needed. Returns success=True on 204 No Content. |
| `MAILERLITE_EXECUTE_BATCH_REQUEST` | Execute Batch Request | Tool to execute multiple API requests in a single batch call (max 50 requests). Use when you need to perform multiple operations efficiently or reduce API call overhead. Note: Individual request failures don't stop batch processing; check each response code. Webhooks are not supported in batch requests. |
| `MAILERLITE_FORGET_SUBSCRIBER` | Forget Subscriber | Tool to forget a subscriber completely (GDPR compliant deletion). Use when you need to permanently delete all subscriber data within 30 days. |
| `MAILERLITE_GET_ACCOUNT_INFO` | Get Account Info | Tool to retrieve basic MailerLite account details. Use when you need to verify authentication and review account metadata. Response payload is nested under results[i].response.data with data and meta subkeys — not a flat data key. Does not return a dedicated sender-domain list; absent domain fields indicate unknown status, not verified or unverified. |
| `MAILERLITE_GET_ACCOUNT_STATS` | Get Account Stats | Tool to retrieve usage statistics and performance metrics for the account. Use after sending campaigns to analyze engagement and deliverability. |
| `MAILERLITE_GET_AUTOMATION` | Get Automation | Tool to retrieve details of a specific automation by ID. Use when you have the automation ID and need its full configuration. Example: "Get automation 7267552". |
| `MAILERLITE_GET_AUTOMATION_ACTIVITY` | Get Automation Activity | Tool to retrieve subscriber activity for a specific automation. Use when you need to track automation execution status and subscriber progress through workflows. Requires filter[status] parameter to be specified. |
| `MAILERLITE_GET_CAMPAIGN_LANGUAGES` | Get Campaign Languages | Tool to retrieve a list of all available campaign languages. Use when you need to fetch supported languages for creating or configuring campaigns. |
| `MAILERLITE_GET_CAMPAIGNS` | Get Campaigns | Tool to retrieve a list of all campaigns. Use when you need to fetch campaigns optionally filtered by status or type, with pagination. |
| `MAILERLITE_GET_ECOMMERCE_CART` | Get E-commerce Cart | Tool to fetch details of a specific cart by shop ID and cart ID. Use when you need to retrieve cart information including customer, items, total, and checkout URL. |
| `MAILERLITE_GET_ECOMMERCE_CART_ITEM` | Get E-commerce Cart Item | Tool to fetch details of a specific cart item by shop ID, cart ID, and item ID. Use when you need to retrieve information about a specific item in a cart. |
| `MAILERLITE_GET_ECOMMERCE_CATEGORY` | Get E-commerce Category | Tool to fetch details of a specific product category by shop and category ID. Use when you need information about a specific e-commerce category. |
| `MAILERLITE_GET_ECOMMERCE_CUSTOMER` | Get E-commerce Customer | Tool to fetch details of a customer by shop and customer ID. Use after confirming shop_id and customer_id. |
| `MAILERLITE_GET_ECOMMERCE_CUSTOMERS` | Get E-commerce Customers | Tool to list customers for a specific shop. Use when you need to retrieve and paginate ecommerce customers after you have a shop ID. Example: "List customers for shop 123". |
| `MAILERLITE_GET_ECOMMERCE_ORDER` | Get E-commerce Order | Tool to fetch details of a specific e-commerce order by shop ID and order ID. Use when you need to retrieve order information including customer, cart items, total, and status. |
| `MAILERLITE_GET_ECOMMERCE_PRODUCT` | Get E-commerce Product | Tool to fetch details of a specific e-commerce product by shop and product ID. Use when you need product information such as name, price, description, and categories. |
| `MAILERLITE_GET_ECOMMERCE_SHOP` | Get E-commerce Shop | Tool to fetch details of a specific e-commerce shop by ID. Use when you need detailed configuration or stats of a connected shop. |
| `MAILERLITE_GET_ECOMMERCE_SHOPS` | Get E-commerce Shops | Tool to list all e-commerce shops connected to the account. Use when you need to retrieve and paginate shop listings for an account. |
| `MAILERLITE_GET_FIELDS` | Get Fields | Tool to retrieve all custom fields defined in the account. Use when you need to list or paginate through subscriber custom fields. |
| `MAILERLITE_GET_GROUP` | Get Group | Tool to retrieve details of a specific subscriber group by ID. Use when you need information about a particular group's statistics and configuration. |
| `MAILERLITE_GET_GROUPS` | Get Groups | Tool to retrieve all subscriber groups. Use when listing, paginating, or looking up group IDs for use in downstream tools (e.g., `trigger.settings.group_id`). Always verify returned IDs exactly match before passing to other tools; mismatched IDs cause silent failures. |
| `MAILERLITE_GET_GROUP_SUBSCRIBERS` | Get Group Subscribers | Tool to list subscribers within a group by ID. Use when you need to retrieve subscribers belonging to a specific MailerLite group before targeted campaigns. Use after confirming the group ID is valid. |
| `MAILERLITE_GET_IMPORT_STATUS` | Get Import Status | Tool to retrieve the status and detailed report of a subscriber import operation by import ID. Use after initiating an import to track progress and review results including validation issues, duplicates, and processing statistics. |
| `MAILERLITE_GET_SEGMENT` | Get Segment | Tool to retrieve a specific segment by ID. Use when you need to get details about a particular segment including subscriber count, open rate, and click rate statistics. |
| `MAILERLITE_GET_SEGMENTS` | Get Segments | Tool to retrieve all segments in the account. Use when you need to list or paginate through segments. |
| `MAILERLITE_GET_SEGMENT_SUBSCRIBERS` | Get Segment Subscribers | Tool to retrieve all subscribers belonging to a specific segment. Use when you need to list or paginate through subscribers in a MailerLite segment for targeted campaigns or analysis. |
| `MAILERLITE_GET_SUBSCRIBER` | Get Subscriber | Tool to fetch a single subscriber by ID or email address. Use when you need to retrieve detailed information about a specific subscriber. |
| `MAILERLITE_GET_SUBSCRIBER_ACTIVITY` | Get Subscriber Activity | Tool to fetch the activity log for a specific subscriber. Use when you need to track subscriber engagement history including email opens, link clicks, bounces, and other events. |
| `MAILERLITE_GET_SUBSCRIBERS` | Get Subscribers | Tool to retrieve all subscribers. Use after connecting account and when listing subscribers by status or paginating. Response payload nested under results[i].response.data with data and meta subkeys. Paginate all pages before computing metrics to avoid sampling bias. Limited by MailerLite Connect API quotas. |
| `MAILERLITE_GET_SUBSCRIBERS_STATS` | Get Subscribers Stats | Tool to get subscriber statistics for the account. Use to retrieve counts of total, active, unsubscribed, unconfirmed, bounced, and junk subscribers. |
| `MAILERLITE_GET_WEBHOOK` | Get Webhook | Tool to retrieve details of a specific webhook by ID. Use when you need to get information about a particular webhook configuration. |
| `MAILERLITE_GET_WEBHOOKS` | Get Webhooks | Tool to retrieve all configured webhooks. Use when you need to list webhooks for your MailerLite account. |
| `MAILERLITE_IMPORT_ECOMMERCE_CATEGORIES` | Import E-commerce Categories | Tool to bulk import categories to an e-commerce shop. Use when you need to add multiple categories at once to a shop. |
| `MAILERLITE_IMPORT_ECOMMERCE_ORDERS` | Import E-commerce Orders | Tool to bulk import orders to an e-commerce shop. Use when syncing historical orders or bulk loading order data. Products must exist before importing orders. |
| `MAILERLITE_IMPORT_ECOMMERCE_PRODUCTS` | Import E-commerce Products | Tool to bulk import products to an e-commerce shop. Use when you need to add multiple products to a shop in one request. |
| `MAILERLITE_IMPORT_SUBSCRIBERS_TO_GROUP` | Import Subscribers to Group | Tool to bulk import multiple subscribers to a specific group. Use when adding many subscribers at once is more efficient than individual creation. The import runs asynchronously by default; use the returned progress URL to check completion status. |
| `MAILERLITE_LIST_AUTOMATIONS` | List Automations | Tool to retrieve all automations in your MailerLite account. Use when you need to list automations, optionally filtered by status, name, or group. Supports pagination for large result sets. |
| `MAILERLITE_LIST_ECOMMERCE_CART_ITEMS` | List E-commerce Cart Items | Tool to list all items in a specific cart for an e-commerce shop. Use when you need to retrieve items from a cart after you have both a shop ID and cart ID. |
| `MAILERLITE_LIST_ECOMMERCE_CARTS` | List E-commerce Carts | Tool to list all carts for a specific shop. Use when you need to retrieve abandoned or active shopping carts after you have a shop ID. Example: "List carts for shop 49095". |
| `MAILERLITE_LIST_ECOMMERCE_CATEGORIES` | List E-commerce Categories | Tool to list all product categories for a shop. Use when you need to retrieve or paginate through categories. |
| `MAILERLITE_LIST_ECOMMERCE_CATEGORY_PRODUCTS` | List E-commerce Category Products | Tool to list all products in a specific e-commerce category. Use when you need to retrieve products for a given shop and category combination. |
| `MAILERLITE_LIST_ECOMMERCE_ORDERS` | List E-commerce Orders | Tool to list all orders for a specific e-commerce shop. Use when you need to retrieve and paginate orders for a shop after you have a shop ID. |
| `MAILERLITE_LIST_ECOMMERCE_PRODUCTS` | List E-commerce Products | Tool to list all products for a specific e-commerce shop. Use when you need to retrieve and paginate product listings after you have a shop ID. |
| `MAILERLITE_LIST_FORMS` | List Forms | Tool to retrieve all forms of a specific type (popup, embedded, or promotion). Use when you need to list forms with optional filtering by name and pagination support. |
| `MAILERLITE_LIST_TIMEZONES` | List Timezones | Tool to retrieve all available timezones supported by MailerLite. Use when you need to get timezone options for campaigns, automations, or scheduling. |
| `MAILERLITE_REMOVE_PRODUCT_FROM_CATEGORY` | Remove Product From Category | Tool to remove a product from a category in an e-commerce shop. Use when you need to unlink a product from a specific category without deleting the product itself. |
| `MAILERLITE_REMOVE_SUBSCRIBER_FROM_GROUP` | Remove Subscriber From Group | Tool to remove a subscriber from a group by ID. Use when you need to unassign a subscriber from a specific group in your MailerLite account. Returns success=True on 204 No Content. |
| `MAILERLITE_SET_DOUBLE_OPTIN` | Set Double Opt-In | Tool to enable or disable double opt-in for new subscribers. Use when configuring subscription confirmation settings. |
| `MAILERLITE_UPDATE_ECOMMERCE_CART` | Update E-commerce Cart | Tool to update an existing cart's checkout URL or total price. Use when you need to modify cart details like the checkout link or recalculate the cart total for an active shopping cart. |
| `MAILERLITE_UPDATE_ECOMMERCE_CART_ITEM` | Update E-commerce Cart Item | Tool to update a cart item's quantity or properties in an e-commerce cart. Use when you need to modify an existing item in a customer's cart. |
| `MAILERLITE_UPDATE_ECOMMERCE_CATEGORY` | Update E-commerce Category | Tool to update an existing product category in an e-commerce shop. Use when you need to modify the category name or automation settings. |
| `MAILERLITE_UPDATE_ECOMMERCE_CUSTOMER` | Update E-commerce Customer | Tool to update a customer's data for a shop by IDs. Use when you need to change email, marketing opt-in, or spend totals for an existing customer. |
| `MAILERLITE_UPDATE_ECOMMERCE_ORDER` | Update E-commerce Order | Tool to update an existing order's status or total price in an e-commerce shop. Use when you need to mark orders as complete or adjust pricing. Note: Cannot update cart or customer through this endpoint. |
| `MAILERLITE_UPDATE_ECOMMERCE_PRODUCT` | Update E-commerce Product | Tool to update an existing product in an e-commerce shop by IDs. Use when you need to modify product details like name, price, description, or URL. |
| `MAILERLITE_UPDATE_ECOMMERCE_SHOP` | Update E-commerce Shop | Tool to update settings of a connected e-commerce shop by ID. Use when you need to modify shop details (name, URL, currency) or toggle features after verifying the shop exists. |
| `MAILERLITE_UPDATE_FIELD` | Update Field | Tool to update the title of an existing custom field. Use when renaming a field label (e.g., correct typos or rebranding). |
| `MAILERLITE_UPDATE_GROUP` | Update Group | Tool to update a group's name by ID. Use when renaming an existing group after confirming its ID. Note: renaming does not update references in downstream integrations or reports that use the old group name. |
| `MAILERLITE_UPDATE_SEGMENT` | Update Segment | Tool to rename an existing segment by ID. Use when you need to update a segment's name after confirming its ID. |
| `MAILERLITE_UPDATE_SUBSCRIBER` | Update Subscriber | Tool to update an existing subscriber's information by ID. Use when altering subscriber details. |
| `MAILERLITE_UPDATE_WEBHOOK` | Update Webhook | Tool to update an existing MailerLite webhook. Use when you need to change its URL or event triggers by ID. |

## Supported Triggers

None listed.

## Creating MCP Server - Stand-alone vs Composio SDK

The Mailerlite MCP server is an implementation of the Model Context Protocol that connects your AI agent to Mailerlite. It provides structured and secure access so your agent can perform Mailerlite operations on your behalf through a secure, permission-based interface.
With Composio's managed implementation, you don't have to create your own developer app. For production, if you're building an end product, we recommend using your own credentials. The managed server helps you prototype fast and go from 0-1 faster.

## Step-by-step Guide

### 1. Prerequisites

Before you begin, make sure you have:
- Node.js and npm installed
- A Composio account with API key
- An OpenAI API key

### 1. Getting API Keys for OpenAI and Composio

OpenAI API Key
- Go to the [OpenAI dashboard](https://platform.openai.com/settings/organization/api-keys) 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
- Log in to the [Composio dashboard](https://dashboard.composio.dev?utm_source=toolkits&utm_medium=framework_docs).
- Navigate to your API settings and generate a new API key.
- Store this key securely as you'll need it for authentication.

### 2. Install required dependencies

First, install the necessary packages for your project.
What you're installing:
- @ai-sdk/openai: Vercel AI SDK's OpenAI provider
- @ai-sdk/mcp: MCP client for Vercel AI SDK
- @composio/core: Composio SDK for tool integration
- ai: Core Vercel AI SDK
- dotenv: Environment variable management
```bash
npm install @ai-sdk/openai @ai-sdk/mcp @composio/core ai dotenv
```

### 3. Set up environment variables

Create a .env file in your project root.
What's needed:
- OPENAI_API_KEY: Your OpenAI API key for GPT model access
- COMPOSIO_API_KEY: Your Composio API key for tool access
- COMPOSIO_USER_ID: A unique identifier for the user session
```bash
OPENAI_API_KEY=your_openai_api_key_here
COMPOSIO_API_KEY=your_composio_api_key_here
COMPOSIO_USER_ID=your_user_id_here
```

### 4. Import required modules and validate environment

What's happening:
- We're importing all necessary libraries including Vercel AI SDK's OpenAI provider and Composio
- The dotenv/config import automatically loads environment variables
- The MCP client import enables connection to Composio's tool server
```typescript
import "dotenv/config";
import { openai } from "@ai-sdk/openai";
import { Composio } from "@composio/core";
import * as readline from "readline";
import { streamText, type ModelMessage, stepCountIs } from "ai";
import { createMCPClient } from "@ai-sdk/mcp";

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

if (!process.env.OPENAI_API_KEY) 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,
});
```

### 5. Create Tool Router session and initialize MCP client

What's happening:
- We're creating a Tool Router session that gives your agent access to Mailerlite tools
- The create method takes the user ID and specifies which toolkits should be available
- The returned mcp object contains the URL and authentication headers needed to connect to the MCP server
- This session provides access to all Mailerlite-related tools through the MCP protocol
```typescript
async function main() {
  // Create a tool router session for the user
  const session = await composio.create(composioUserID!, {
    toolkits: ["mailerlite"],
  });

  const mcpUrl = session.mcp.url;
```

### 6. Connect to MCP server and retrieve tools

What's happening:
- We're creating an MCP client that connects to our Composio Tool Router session via HTTP
- The mcp.url provides the endpoint, and mcp.headers contains authentication credentials
- The type: "http" is important - Composio requires HTTP transport
- tools() retrieves all available Mailerlite tools that the agent can use
```typescript
const mcpClient = await createMCPClient({
  transport: {
    type: "http",
    url: mcpUrl,
    headers: session.mcp.headers, // Authentication headers for the Composio MCP server
  },
});

const tools = await mcpClient.tools();
```

### 7. Initialize conversation and CLI interface

What's happening:
- We initialize an empty messages array to maintain conversation history
- A readline interface is created to accept user input from the command line
- Instructions are displayed to guide the user on how to interact with the agent
```typescript
let messages: ModelMessage[] = [];

console.log("Chat started! Type 'exit' or 'quit' to end the conversation.\n");
console.log(
  "Ask any questions related to mailerlite, like summarize my last 5 emails, send an email, etc... :)))\n",
);

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

rl.prompt();
```

### 8. Handle user input and stream responses with real-time tool feedback

What's happening:
- We use streamText instead of generateText to stream responses in real-time
- toolChoice: "auto" allows the model to decide when to use Mailerlite tools
- stopWhen: stepCountIs(10) allows up to 10 steps for complex multi-tool operations
- onStepFinish callback displays which tools are being used in real-time
- We iterate through the text stream to create a typewriter effect as the agent responds
- The complete response is added to conversation history to maintain context
- Errors are caught and displayed with helpful retry suggestions
```typescript
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({ role: "user", content: trimmedInput });
  console.log("\nAgent is thinking...\n");

  try {
    const stream = streamText({
      model: openai("gpt-5"),
      messages,
      tools,
      toolChoice: "auto",
      stopWhen: stepCountIs(10),
      onStepFinish: (step) => {
        for (const toolCall of step.toolCalls) {
          console.log(`[Using tool: ${toolCall.toolName}]`);
          }
          if (step.toolCalls.length > 0) {
            console.log(""); // Add space after tool calls
          }
        },
      });

      for await (const chunk of stream.textStream) {
        process.stdout.write(chunk);
      }

      console.log("\n\n---\n");

      // Get final result for message history
      const response = await stream.response;
      if (response?.messages?.length) {
        messages.push(...response.messages);
      }
    } catch (error) {
      console.error("\nAn error occurred while talking to the agent:");
      console.error(error);
      console.log(
        "\nYou can try again or restart the app if it keeps happening.\n",
      );
    } finally {
      rl.prompt();
    }
  });

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

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

## Complete Code

```typescript
import "dotenv/config";
import { openai } from "@ai-sdk/openai";
import { Composio } from "@composio/core";
import * as readline from "readline";
import { streamText, type ModelMessage, stepCountIs } from "ai";
import { createMCPClient } from "@ai-sdk/mcp";

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

if (!process.env.OPENAI_API_KEY) 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,
});

async function main() {
  // Create a tool router session for the user
  const session = await composio.create(composioUserID!, {
    toolkits: ["mailerlite"],
  });

  const mcpUrl = session.mcp.url;

  const mcpClient = await createMCPClient({
    transport: {
      type: "http",
      url: mcpUrl,
      headers: session.mcp.headers, // Authentication headers for the Composio MCP server
    },
  });

  const tools = await mcpClient.tools();

  let messages: ModelMessage[] = [];

  console.log("Chat started! Type 'exit' or 'quit' to end the conversation.\n");
  console.log(
    "Ask any questions related to mailerlite, like summarize my last 5 emails, send an email, etc... :)))\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({ role: "user", content: trimmedInput });
    console.log("\nAgent is thinking...\n");

    try {
      const stream = streamText({
        model: openai("gpt-5"),
        messages,
        tools,
        toolChoice: "auto",
        stopWhen: stepCountIs(10),
        onStepFinish: (step) => {
          for (const toolCall of step.toolCalls) {
            console.log(`[Using tool: ${toolCall.toolName}]`);
          }
          if (step.toolCalls.length > 0) {
            console.log(""); // Add space after tool calls
          }
        },
      });

      for await (const chunk of stream.textStream) {
        process.stdout.write(chunk);
      }

      console.log("\n\n---\n");

      // Get final result for message history
      const response = await stream.response;
      if (response?.messages?.length) {
        messages.push(...response.messages);
      }
    } catch (error) {
      console.error("\nAn error occurred while talking to the agent:");
      console.error(error);
      console.log(
        "\nYou can try again or restart the app if it keeps happening.\n",
      );
    } finally {
      rl.prompt();
    }
  });

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

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

## Conclusion

You've successfully built a Mailerlite agent using the Vercel AI SDK with streaming capabilities! This implementation provides a powerful foundation for building AI applications with natural language interfaces and real-time feedback.
Key features of this implementation:
- Real-time streaming responses for a better user experience with typewriter effect
- Live tool execution feedback showing which tools are being used as the agent works
- Dynamic tool loading through Composio's Tool Router with secure authentication
- Multi-step tool execution with configurable step limits (up to 10 steps)
- Comprehensive error handling for robust agent execution
- Conversation history maintenance for context-aware responses
You can extend this further by adding custom error handling, implementing specific business logic, or integrating additional Composio toolkits to create multi-app workflows.

## How to build Mailerlite MCP Agent with another framework

- [OpenAI Agents SDK](https://composio.dev/toolkits/mailerlite/framework/open-ai-agents-sdk)
- [Claude Agent SDK](https://composio.dev/toolkits/mailerlite/framework/claude-agents-sdk)
- [Claude Code](https://composio.dev/toolkits/mailerlite/framework/claude-code)
- [Claude Cowork](https://composio.dev/toolkits/mailerlite/framework/claude-cowork)
- [Codex](https://composio.dev/toolkits/mailerlite/framework/codex)
- [OpenClaw](https://composio.dev/toolkits/mailerlite/framework/openclaw)
- [Hermes](https://composio.dev/toolkits/mailerlite/framework/hermes-agent)
- [CLI](https://composio.dev/toolkits/mailerlite/framework/cli)
- [Google ADK](https://composio.dev/toolkits/mailerlite/framework/google-adk)
- [LangChain](https://composio.dev/toolkits/mailerlite/framework/langchain)
- [Mastra AI](https://composio.dev/toolkits/mailerlite/framework/mastra-ai)
- [LlamaIndex](https://composio.dev/toolkits/mailerlite/framework/llama-index)
- [CrewAI](https://composio.dev/toolkits/mailerlite/framework/crew-ai)

## Related Toolkits

- [Reddit](https://composio.dev/toolkits/reddit) - Reddit is a social news platform with thriving user-driven communities (subreddits). It's the go-to place for discussion, content sharing, and viral marketing.
- [Facebook](https://composio.dev/toolkits/facebook) - Facebook is a social media and advertising platform for businesses and creators. It helps you connect, share, and manage content across your public Facebook Pages.
- [Linkedin](https://composio.dev/toolkits/linkedin) - LinkedIn is a professional networking platform for connecting, sharing content, and engaging with business opportunities. It's the go-to place for building your professional brand and unlocking new career connections.
- [Active campaign](https://composio.dev/toolkits/active_campaign) - ActiveCampaign is a marketing automation and CRM platform for managing email campaigns, sales pipelines, and customer segmentation. It helps businesses engage customers and drive growth through smart automation and targeted outreach.
- [ActiveTrail](https://composio.dev/toolkits/active_trail) - ActiveTrail is a user-friendly email marketing and automation platform. It helps you reach subscribers and automate campaigns with ease.
- [Ahrefs](https://composio.dev/toolkits/ahrefs) - Ahrefs is an SEO and marketing platform for site audits, keyword research, and competitor insights. It helps you improve search rankings and drive organic traffic.
- [Amcards](https://composio.dev/toolkits/amcards) - AMCards lets you create and mail personalized greeting cards online. Build stronger customer relationships with easy, automated card campaigns.
- [Beamer](https://composio.dev/toolkits/beamer) - Beamer is a news and changelog platform for in-app announcements and feature updates. It helps companies boost user engagement by sharing news where users are most active.
- [Benchmark email](https://composio.dev/toolkits/benchmark_email) - Benchmark Email is a platform for creating, sending, and tracking email campaigns. It's built to help you engage audiences and analyze results—all in one place.
- [Bigmailer](https://composio.dev/toolkits/bigmailer) - BigMailer is an email marketing platform for managing multiple brands with white-labeling and automation. It helps teams streamline campaigns and simplify integration with Amazon SES.
- [Brandfetch](https://composio.dev/toolkits/brandfetch) - Brandfetch is an API that delivers company logos, colors, and visual branding assets. It helps marketers and developers keep brand visuals consistent everywhere.
- [Brevo](https://composio.dev/toolkits/brevo) - Brevo is an all-in-one email and SMS marketing platform for transactional messaging, automation, and CRM. It helps businesses engage customers and streamline communications through powerful campaign tools.
- [Campayn](https://composio.dev/toolkits/campayn) - Campayn is an email marketing platform for creating, sending, and managing campaigns. It helps businesses engage contacts and grow audiences with easy-to-use tools.
- [Cardly](https://composio.dev/toolkits/cardly) - Cardly is a platform for creating and sending personalized direct mail to customers. It helps businesses break through the digital clutter by getting real engagement via physical mailboxes.
- [ClickSend](https://composio.dev/toolkits/clicksend) - ClickSend is a cloud-based SMS and email marketing platform for businesses. It streamlines communication by enabling quick message delivery and contact management.
- [Crustdata](https://composio.dev/toolkits/crustdata) - CrustData is an AI-powered data intelligence platform for real-time company and people data. It helps B2B sales teams, AI SDRs, and investors react to live business signals.
- [Curated](https://composio.dev/toolkits/curated) - Curated is a platform for collecting, curating, and publishing newsletters. It streamlines content aggregation and distribution for creators and teams.
- [Customerio](https://composio.dev/toolkits/customerio) - Customer.io is a customer engagement platform for targeted messaging across email, SMS, and push. Easily automate, segment, and track communications with your audience.
- [Cutt ly](https://composio.dev/toolkits/cutt_ly) - Cutt.ly is a URL shortening service for managing and analyzing links. Streamline your workflows with quick, trackable, and branded short URLs.
- [Demio](https://composio.dev/toolkits/demio) - Demio is webinar software built for marketers, offering both live and automated sessions with interactive features. It helps teams engage audiences and optimize lead generation through detailed analytics.

## Frequently Asked Questions

### What are the differences in Tool Router MCP and Mailerlite MCP?

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.

### Can I use Tool Router MCP with Vercel AI SDK v6?

Yes, you can. Vercel AI SDK v6 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.

### Can I manage the permissions and scopes for Mailerlite while using Tool Router?

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.

### How safe is my data with Composio Tool Router?

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.

---
[See all toolkits](https://composio.dev/toolkits) · [Composio docs](https://docs.composio.dev/llms.txt)