How to integrate Handwrytten MCP with Pydantic AI

GET STARTED FOR FREE
Framework Integration Gradient
Handwrytten Logo
Pydantic AI Logo
divider

Introduction

This guide walks you through connecting Handwrytten to Pydantic 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 Pydantic 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:
  • How to set up your Composio API key and User ID
  • How to create a Composio Tool Router session for Handwrytten
  • How to attach an MCP Server to a Pydantic AI agent
  • How to stream responses and maintain chat history
  • How to build a simple REPL-style chat interface to test your Handwrytten workflows

What is Pydantic AI?

Pydantic AI is a Python framework for building AI agents with strong typing and validation. It leverages Pydantic's data validation capabilities to create robust, type-safe AI applications.

Key features include:

  • Type Safety: Built on Pydantic for automatic data validation
  • MCP Support: Native support for Model Context Protocol servers
  • Streaming: Built-in support for streaming responses
  • Async First: Designed for async/await patterns

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:
  • Python 3.9 or higher
  • A Composio account with an active API key
  • Basic familiarity with Python and async programming

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
  • Log in to the Composio dashboard.
  • Navigate to your API settings and generate a new API key.
  • Store this key securely as you'll need it for authentication.

Install dependencies

bash
pip install composio pydantic-ai python-dotenv

Install the required libraries.

What's happening:

  • composio connects your agent to external SaaS tools like Handwrytten
  • pydantic-ai lets you create structured AI agents with tool support
  • python-dotenv loads your environment variables securely from a .env file

Set up environment variables

bash
COMPOSIO_API_KEY=your_composio_api_key_here
USER_ID=your_user_id_here
OPENAI_API_KEY=your_openai_api_key

Create a .env file in your project root.

What's happening:

  • COMPOSIO_API_KEY authenticates your agent to Composio's API
  • USER_ID associates your session with your account for secure tool access
  • OPENAI_API_KEY to access OpenAI LLMs

Import dependencies

python
import asyncio
import os
from dotenv import load_dotenv
from composio import Composio
from pydantic_ai import Agent
from pydantic_ai.mcp import MCPServerStreamableHTTP

load_dotenv()
What's happening:
  • We load environment variables and import required modules
  • Composio manages connections to Handwrytten
  • MCPServerStreamableHTTP connects to the Handwrytten MCP server endpoint
  • Agent from Pydantic AI lets you define and run the AI assistant

Create a Tool Router Session

python
async def main():
    api_key = os.getenv("COMPOSIO_API_KEY")
    user_id = os.getenv("USER_ID")
    if not api_key or not user_id:
        raise RuntimeError("Set COMPOSIO_API_KEY and USER_ID in your environment")

    # Create a Composio Tool Router session for Handwrytten
    composio = Composio(api_key=api_key)
    session = composio.create(
        user_id=user_id,
        toolkits=["handwrytten"],
    )
    url = session.mcp.url
    if not url:
        raise ValueError("Composio session did not return an MCP URL")
What's happening:
  • We're creating a Tool Router session that gives your agent access to Handwrytten tools
  • The create method takes the user ID and specifies which toolkits should be available
  • The returned session.mcp.url is the MCP server URL that your agent will use

Initialize the Pydantic AI Agent

python
# Attach the MCP server to a Pydantic AI Agent
handwrytten_mcp = MCPServerStreamableHTTP(url, headers={"x-api-key": COMPOSIO_API_KEY})
agent = Agent(
    "openai:gpt-5",
    toolsets=[handwrytten_mcp],
    instructions=(
        "You are a Handwrytten assistant. Use Handwrytten tools to help users "
        "with their requests. Ask clarifying questions when needed."
    ),
)
What's happening:
  • The MCP client connects to the Handwrytten endpoint
  • The agent uses GPT-5 to interpret user commands and perform Handwrytten operations
  • The instructions field defines the agent's role and behavior

Build the chat interface

python
# Simple REPL with message history
history = []
print("Chat started! Type 'exit' or 'quit' to end.\n")
print("Try asking the agent to help you with Handwrytten.\n")

while True:
    user_input = input("You: ").strip()
    if user_input.lower() in {"exit", "quit", "bye"}:
        print("\nGoodbye!")
        break
    if not user_input:
        continue

    print("\nAgent is thinking...\n", flush=True)

    async with agent.run_stream(user_input, message_history=history) as stream_result:
        collected_text = ""
        async for chunk in stream_result.stream_output():
            text_piece = None
            if isinstance(chunk, str):
                text_piece = chunk
            elif hasattr(chunk, "delta") and isinstance(chunk.delta, str):
                text_piece = chunk.delta
            elif hasattr(chunk, "text"):
                text_piece = chunk.text
            if text_piece:
                collected_text += text_piece
        result = stream_result

    print(f"Agent: {collected_text}\n")
    history = result.all_messages()
What's happening:
  • The agent reads input from the terminal and streams its response
  • Handwrytten API calls happen automatically under the hood
  • The model keeps conversation history to maintain context across turns

Run the application

python
if __name__ == "__main__":
    asyncio.run(main())
What's happening:
  • The asyncio loop launches the agent and keeps it running until you exit

Complete Code

Here's the complete code to get you started with Handwrytten and Pydantic AI:

python
import asyncio
import os
from dotenv import load_dotenv
from composio import Composio
from pydantic_ai import Agent
from pydantic_ai.mcp import MCPServerStreamableHTTP

load_dotenv()

async def main():
    api_key = os.getenv("COMPOSIO_API_KEY")
    user_id = os.getenv("USER_ID")
    if not api_key or not user_id:
        raise RuntimeError("Set COMPOSIO_API_KEY and USER_ID in your environment")

    # Create a Composio Tool Router session for Handwrytten
    composio = Composio(api_key=api_key)
    session = composio.create(
        user_id=user_id,
        toolkits=["handwrytten"],
    )
    url = session.mcp.url
    if not url:
        raise ValueError("Composio session did not return an MCP URL")

    # Attach the MCP server to a Pydantic AI Agent
    handwrytten_mcp = MCPServerStreamableHTTP(url, headers={"x-api-key": COMPOSIO_API_KEY})
    agent = Agent(
        "openai:gpt-5",
        toolsets=[handwrytten_mcp],
        instructions=(
            "You are a Handwrytten assistant. Use Handwrytten tools to help users "
            "with their requests. Ask clarifying questions when needed."
        ),
    )

    # Simple REPL with message history
    history = []
    print("Chat started! Type 'exit' or 'quit' to end.\n")
    print("Try asking the agent to help you with Handwrytten.\n")

    while True:
        user_input = input("You: ").strip()
        if user_input.lower() in {"exit", "quit", "bye"}:
            print("\nGoodbye!")
            break
        if not user_input:
            continue

        print("\nAgent is thinking...\n", flush=True)

        async with agent.run_stream(user_input, message_history=history) as stream_result:
            collected_text = ""
            async for chunk in stream_result.stream_output():
                text_piece = None
                if isinstance(chunk, str):
                    text_piece = chunk
                elif hasattr(chunk, "delta") and isinstance(chunk.delta, str):
                    text_piece = chunk.delta
                elif hasattr(chunk, "text"):
                    text_piece = chunk.text
                if text_piece:
                    collected_text += text_piece
            result = stream_result

        print(f"Agent: {collected_text}\n")
        history = result.all_messages()

if __name__ == "__main__":
    asyncio.run(main())

Conclusion

You've built a Pydantic AI agent that can interact with Handwrytten through Composio's Tool Router. With this setup, your agent can perform real Handwrytten actions through natural language. You can extend this further by:
  • Adding other toolkits like Gmail, HubSpot, or Salesforce
  • Building a web-based chat interface around this agent
  • Using multiple MCP endpoints to enable cross-app workflows (for example, Gmail + Handwrytten for workflow automation)
This architecture makes your AI agent "agent-native", able to securely use APIs in a unified, composable way without custom integrations.

How to build Handwrytten MCP Agent with another framework

OpenAI Agents SDK

OpenAI Agents SDK

Use Handwrytten MCP with OpenAI Agents SDK

Claude Agent SDK

Claude Agent SDK

Use Handwrytten MCP with Claude Agent SDK

Google ADK

Google ADK

Use Handwrytten MCP with Google ADK

LangChain

LangChain

Use Handwrytten MCP with LangChain

Vercel AI SDK

Vercel AI SDK

Use Handwrytten MCP with Vercel AI SDK

Mastra AI

Mastra AI

Use Handwrytten MCP with Mastra AI

LlamaIndex

LlamaIndex

Use Handwrytten MCP with LlamaIndex

CrewAI

CrewAI

Use Handwrytten MCP with CrewAI

Claude Code

Claude Code

Use Handwrytten MCP with Claude Code

Codex

Codex

Use Handwrytten MCP with Codex

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 Pydantic AI?

Yes, you can. Pydantic 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.

Used by agents from

Context
Letta
glean
HubSpot
Agent.ai
Altera
DataStax
Entelligence
Rolai
Context
Letta
glean
HubSpot
Agent.ai
Altera
DataStax
Entelligence
Rolai
Context
Letta
glean
HubSpot
Agent.ai
Altera
DataStax
Entelligence
Rolai

Never worry about agent reliability

We handle tool reliability, observability, and security so you never have to second-guess an agent action.

Book a call↗Get started for free