How to integrate Handwrytten MCP with Mastra AI

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Introduction

This guide walks you through connecting Handwrytten to Mastra AI using the Composio tool router. By the end, you'll have a working Handwrytten agent that can send a thank you card to john doe, schedule a handwritten birthday note delivery, list all pending handwrytten orders through natural language commands.

This guide will help you understand how to give your Mastra AI agent real control over a Handwrytten account through Composio's Handwrytten MCP server.

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

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 Handwrytten tools
  • Connect Mastra's MCP client to the Composio generated MCP URL
  • Fetch Handwrytten 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 Handwrytten 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 Handwrytten MCP server, and what's possible with it?

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

Supported Tools & Triggers

Tools
Add RecipientTool to add a recipient address to the user's addressbook in Handwrytten.
Calculate Order TaxesTool to calculate taxes for Handwrytten basket orders.
Check AuthenticationTool to verify API key authentication validity for Handwrytten.
Clear BasketTool to clear all items from the shopping basket.
Create TemplateTool to create a new template for the current user.
Create User AddressTool to create a new user address in Handwrytten.
Delete Custom ImageTool to delete a custom image/logo from Handwrytten.
Delete Recipient AddressTool to delete one or more recipient addresses from user's profile.
Delete TemplateTool to delete a user's template by its ID.
Get Basket (New Method)Tool to retrieve the user's basket using the new method.
Get Basket CountTool to retrieve the count of items currently in the basket.
Get Basket ItemTool to retrieve a basket item by its ID from Handwrytten.
Get Card DetailsTool to get detailed information about a specific card in the Handwrytten catalog.
Get List of AddressesTool to retrieve a list of all addresses associated with the user's account.
Get Random CardsTool to retrieve random cards from Handwrytten.
Get Template DetailsTool to get detailed information about a card text template in the Handwrytten catalog.
Get Current User InfoTool to retrieve information about the currently authenticated user.
Get User AddressTool to retrieve the authenticated user's address and billing information.
List Basket Orders GroupedTool to list all basket orders grouped by basket.
List Past BasketsTool to retrieve a list of user's past baskets.
List CardsTool to retrieve a list of available Handwrytten cards with optional filtering and pagination.
List CategoriesTool to retrieve the list of available card categories from Handwrytten.
List CountriesTool to retrieve the list of countries available in Handwrytten.
List Credit CardsTool to list all credit cards associated with the Handwrytten account.
List FontsTool to retrieve the list of available handwriting fonts.
List Fonts for CustomizerTool to list fonts available for use with the card customizer.
List Gift CardsTool to retrieve the list of available gift cards with their denominations and pricing.
List Custom User ImagesTool to retrieve a list of custom user images uploaded to Handwrytten.
List InsertsTool to retrieve a list of available inserts from Handwrytten.
List OrdersTool to retrieve a list of user's past orders from Handwrytten.
List Orders GroupedTool to retrieve the user's order history grouped by basket.
List Past OrdersTool to retrieve a list of user's past orders from Handwrytten API.
List RecipientsTool to retrieve a list of recipient addresses that the user has previously saved.
List SignaturesTool to retrieve the list of available signatures for use in card orders.
List StatesTool to retrieve the list of states/provinces available in Handwrytten.
List Template CategoriesTool to retrieve the list of available template categories from Handwrytten.
List TemplatesTool to retrieve a list of card text templates from Handwrytten.
Logout UserTool to logout user from Handwrytten application.
Place Order in BasketTool to add an order to the basket in Handwrytten.
Register UserTool to register a new Handwrytten user account.
Request Password ResetTool to request a password reset email for a Handwrytten account.
Set Default AddressTool to set a default return address for the user in Handwrytten.
Set Test ModeTool to set test mode for the current Handwrytten user.
Update Basket ItemTool to update an existing basket item in Handwrytten.
Update Billing InformationTool to update user billing information (country, zip, address) for tax calculations in Handwrytten.
Update RecipientTool to update a recipient address in the user's addressbook in Handwrytten.
Update TemplateTool to update an existing user template in Handwrytten.
Upload Custom LogoTool to upload a custom image (logo or cover) to Handwrytten for use with custom cards.

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

What is Tool Router?

Composio's Tool Router 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 Tool Router

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

How the Tool Router works

The Tool Router 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

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

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 Handwrytten through MCP.

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

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

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

Create a Tool Router session for Handwrytten

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

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

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 Handwrytten toolkit

Create the Mastra agent

typescript
const agent = new Agent({
    name: "handwrytten-mastra-agent",
    instructions: "You are an AI agent with Handwrytten 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

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: {
        handwrytten: 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 Handwrytten 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 Handwrytten 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: ["handwrytten"],
  });

  const composioMCPUrl = session.mcp.url;

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

  const composioTools = await mcpClient.getTools();

  const agent = new Agent({
    name: "handwrytten-mastra-agent",
    instructions: "You are an AI agent with Handwrytten 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: { handwrytten: 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 Handwrytten 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

How to build Handwrytten MCP Agent with another framework

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Vercel AI SDK

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Codex

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FAQ

What are the differences in Tool Router MCP and Handwrytten MCP?

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

Can I use Tool Router MCP with Mastra AI?

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 Handwrytten tools.

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

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

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