How to integrate Kit MCP with Pydantic AI

This guide walks you through connecting Kit to Pydantic AI using the Composio tool router. By the end, you'll have a working Kit agent that can add new subscriber to your welcome form, create a custom field for subscriber notes, delete an outdated broadcast by its id through natural language commands. This guide will help you understand how to give your Pydantic AI agent real control over a Kit account through Composio's Kit MCP server. Before we dive in, let's take a quick look at the key ideas and tools involved.

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Introduction

This guide walks you through connecting Kit to Pydantic AI using the Composio tool router. By the end, you'll have a working Kit agent that can add new subscriber to your welcome form, create a custom field for subscriber notes, delete an outdated broadcast by its id through natural language commands.

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

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

Also integrate Kit with

OpenAI Agents SDKClaude Agent SDKClaude CodeClaude CoworkCodexOpenClawHermesCLIGoogle ADKLangChainVercel AI SDKMastra AILlamaIndexCrewAI

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 Kit
  • 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 Kit 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 Kit MCP server, and what's possible with it?

The Kit MCP server is an implementation of the Model Context Protocol that connects your AI agent and assistants like Claude, Cursor, etc directly to your Kit account. It provides structured and secure access to your subscriber lists, tags, forms, and automations, so your agent can perform actions like managing subscribers, creating tags, updating custom fields, and handling broadcasts on your behalf.

  • Subscriber management and automation: Add new subscribers to forms, remove subscribers, or update their details to keep your audience lists accurate and engaged.
  • Custom field and tag creation: Automatically create, update, or delete custom fields and tags, making it easy to segment and personalize your communications.
  • Webhook and event setup: Set up or remove webhooks so your agent can listen for subscriber or purchase events and trigger automations as needed.
  • Broadcast and campaign control: Delete obsolete broadcasts or manage your messaging campaigns directly through your agent for streamlined outreach.
  • Account insights and configuration: Retrieve detailed account information, including plan details and primary contact, to keep your integrations and automations running smoothly.

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:
  • Python 3.9 or higher
  • A Composio account with an active API key
  • Basic familiarity with Python and async programming
2

Getting API Keys for OpenAI and Composio

OpenAI API Key
  • Go to the OpenAI dashboard and create an API key. You'll need credits to use the models, or you can connect to another model provider.
  • Keep the API key safe.
Composio API Key
  • 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.
3

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 Kit
  • pydantic-ai lets you create structured AI agents with tool support
  • python-dotenv loads your environment variables securely from a .env file
4

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
5

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 Kit
  • MCPServerStreamableHTTP connects to the Kit MCP server endpoint
  • Agent from Pydantic AI lets you define and run the AI assistant
6

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 Kit
    composio = Composio(api_key=api_key)
    session = composio.create(
        user_id=user_id,
        toolkits=["kit"],
    )
    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 Kit 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
7

Initialize the Pydantic AI Agent

python
# Attach the MCP server to a Pydantic AI Agent
kit_mcp = MCPServerStreamableHTTP(url, headers={"x-api-key": COMPOSIO_API_KEY})
agent = Agent(
    "openai:gpt-5",
    toolsets=[kit_mcp],
    instructions=(
        "You are a Kit assistant. Use Kit tools to help users "
        "with their requests. Ask clarifying questions when needed."
    ),
)
What's happening:
  • The MCP client connects to the Kit endpoint
  • The agent uses GPT-5 to interpret user commands and perform Kit operations
  • The instructions field defines the agent's role and behavior
8

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 Kit.\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
  • Kit API calls happen automatically under the hood
  • The model keeps conversation history to maintain context across turns
9

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 Kit 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 Kit
    composio = Composio(api_key=api_key)
    session = composio.create(
        user_id=user_id,
        toolkits=["kit"],
    )
    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
    kit_mcp = MCPServerStreamableHTTP(url, headers={"x-api-key": COMPOSIO_API_KEY})
    agent = Agent(
        "openai:gpt-5",
        toolsets=[kit_mcp],
        instructions=(
            "You are a Kit assistant. Use Kit 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 Kit.\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 Kit through Composio's Tool Router. With this setup, your agent can perform real Kit 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 + Kit for workflow automation)
This architecture makes your AI agent "agent-native", able to securely use APIs in a unified, composable way without custom integrations.
TOOLS

Supported Tools

Every Kit action and event your agent gets out of the box.

Add Subscriber to Form

Add an existing subscriber to a form by their IDs.

Add Subscriber to Form by Email

Tool to add an existing subscriber to a form using their email address.

Create Broadcast

Tool to create a new broadcast (email campaign) to send to subscribers.

Create Custom Field

Tool to create a new custom field for subscriber data.

Create Subscriber

Tool to create a new subscriber or update an existing one (upsert).

Create Tag

Tool to create a new tag in the account.

Create Webhook

Creates a webhook subscription for real-time event notifications.

Delete Broadcast

Tool to delete a specific broadcast.

Delete Custom Field

Tool to delete a specific custom field.

Delete Subscriber

Unsubscribe a subscriber from all email communications by their ID.

Delete Tag

Tool to delete a tag by ID.

Delete Webhook

Tool to delete a webhook by ID.

Filter Subscribers

Tool to filter subscribers based on engagement criteria such as email opens, clicks, or delivery status.

Get Account

Tool to retrieve current account information.

Get Account Colors

Tool to retrieve list of colors associated with the account.

Get Broadcast

Tool to retrieve details of a specific broadcast by ID.

Get Broadcast Clicks

Tool to retrieve link click data for a specific broadcast by ID.

Get Broadcast Stats

Tool to retrieve statistics for a specific broadcast by ID.

Get Creator Profile

Tool to retrieve the creator profile information for the account.

Get Email Stats

Tool to retrieve email statistics for the account.

Get Growth Stats

Tool to retrieve growth statistics for the account over a date range.

Get Subscriber

Tool to retrieve a specific subscriber by their ID.

Get Subscriber Stats

Tool to retrieve email stats for a specific subscriber.

List Broadcasts

Tool to retrieve a paginated list of all broadcasts.

List Custom Fields

Tool to retrieve a paginated list of custom fields.

List Email Templates

Retrieve a paginated list of all email templates in the Kit account.

List Forms

Lists all forms in your Kit account with optional filtering and cursor-based pagination.

List Segments

Tool to retrieve a paginated list of segments.

List Sequences

Tool to retrieve a paginated list of all sequences.

List Subscribers

Tool to retrieve a list of subscribers.

List Subscribers For Form

Retrieves subscribers for a specific form by ID with optional filtering and cursor-based pagination.

List Tags

Retrieve a paginated list of all tags in the Kit account.

List Tag Subscribers

Tool to retrieve subscribers for a specific tag.

List Webhooks

Retrieve a paginated list of all webhooks configured in the Kit account.

Remove Tag From Subscriber

Tool to remove a tag from a subscriber using their subscriber ID.

Tag Subscriber

Tool to associate a subscriber with a specific tag by ID.

Tag Subscriber by Email

Assigns a tag to an existing subscriber using their email address.

Untag Subscriber by Email

Tool to remove a tag from a subscriber using their email address.

Update Account Colors

Tool to update the list of colors for the account.

Update Custom Field

Tool to update a custom field's label.

Update Subscriber

Tool to update an existing subscriber's information.

Update Tag

Tool to update a tag's name by ID.

FRAMEWORKS

How to build Kit MCP Agent with another framework

OpenAI Agents SDK logo

OpenAI Agents SDK

Use Kit MCP with OpenAI Agents SDK

Claude Agent SDK logo

Claude Agent SDK

Use Kit MCP with Claude Agent SDK

Claude Code logo

Claude Code

Use Kit MCP with Claude Code

Claude Cowork logo

Claude Cowork

Use Kit MCP with Claude Cowork

Codex logo

Codex

Use Kit MCP with Codex

OpenClaw logo

OpenClaw

Use Kit MCP with OpenClaw

Hermes logo

Hermes

Use Kit MCP with Hermes

CLI logo

CLI

Use Kit MCP with CLI

Google ADK logo

Google ADK

Use Kit MCP with Google ADK

LangChain logo

LangChain

Use Kit MCP with LangChain

Vercel AI SDK logo

Vercel AI SDK

Use Kit MCP with Vercel AI SDK

Mastra AI logo

Mastra AI

Use Kit MCP with Mastra AI

LlamaIndex logo

LlamaIndex

Use Kit MCP with LlamaIndex

CrewAI logo

CrewAI

Use Kit MCP with CrewAI

FAQ

Frequently asked questions

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

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 Kit tools.

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

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

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

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