How to integrate Affinity MCP with Pydantic AI

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Introduction

This guide walks you through connecting Affinity to Pydantic AI using the Composio tool router. By the end, you'll have a working Affinity agent that can list all companies added this week, show all opportunities in active pipeline, get recent contacts linked to acme corp, summarize all lists where john doe appears through natural language commands.

This guide will help you understand how to give your Pydantic AI agent real control over a Affinity account through Composio's Affinity 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 Affinity
  • 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 Affinity 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 Affinity MCP server, and what's possible with it?

The Affinity MCP server is an implementation of the Model Context Protocol that connects your AI agent and assistants like Claude, Cursor, etc directly to your Affinity account. It provides structured and secure access to your deal, company, and contact data, so your agent can analyze lists, fetch opportunity details, extract company insights, and organize people or organizations on your behalf.

  • Company data extraction and analysis: Let your agent retrieve detailed company profiles, summarize list entries, and pull custom field data for deeper insights and reporting.
  • Opportunity pipeline management: Automatically fetch and review all ongoing opportunities, track changes, and surface high-priority deals for follow-up.
  • List and view organization: Ask your agent to access entries across lists or saved views, aggregating metadata and field values for efficient CRM workflows.
  • Contact and relationship intelligence: Effortlessly browse, analyze, and summarize person records, including their list memberships, activity, and custom fields.
  • Automated CRM reporting: Generate summaries, export data, and monitor changes across companies, people, and opportunities to keep your pipeline up-to-date and actionable.

Supported Tools & Triggers

Tools
Get a company s list entriesSummarize company data across all lists, including list-specific fields and metadata like creation date and author.
Get a company s listsReturns metadata for all the lists on which the given company appears.
Get all companiesAffinity api allows paginated access to company info and custom fields.
Get all list entries on a listAccess and export essential data and metadata for companies, persons, or opportunities from a list, specifying data via `fieldids` or `fieldtypes`.
Get all list entries on a saved viewUse the endpoint to access rows in a saved view with specific filters and selected fields from a web app.
Get all opportunitiesPagination through opportunities in affinity yields basic info but excludes field data.
Get all personsThe affinity api offers paginated access to person data using `fieldids` or `fieldtypes`.
Get a person s list entriesSummary: browse rows for a person in all lists, showing field data and entry metadata like creation time and author.
Get a person s listsReturns metadata for all the lists on which the given person appears.
Get a single companyRetrieve basic company info and specific field data by using `fieldids` or `fieldtypes` parameters.
Get a single opportunityGet basic details about an opportunity without field data via provided endpoints.
Get a single personUse get `/v2/persons/fields` with `fieldids` or `fieldtypes` for detailed data; basic info by default.
Get current userReturns metadata about the current user.
Get metadata on all listsReturns metadata on lists.
Get metadata on a single listReturns metadata on a single list.
Get metadata on a single list s fieldsReturns metadata on the fields available on a single list.
Get metadata on a single saved viewReturns metadata on a single saved view.
Get metadata on company fieldsReturns metadata on non-list-specific company fields.
Get metadata on person fieldsReturns metadata on non-list-specific person fields.
Get metadata on saved viewsReturns metadata on the saved views on a list.

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 Affinity
  • 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 Affinity
  • MCPServerStreamableHTTP connects to the Affinity 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 Affinity
    composio = Composio(api_key=api_key)
    session = composio.create(
        user_id=user_id,
        toolkits=["affinity"],
    )
    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 Affinity 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
affinity_mcp = MCPServerStreamableHTTP(url, headers={"x-api-key": COMPOSIO_API_KEY})
agent = Agent(
    "openai:gpt-5",
    toolsets=[affinity_mcp],
    instructions=(
        "You are a Affinity assistant. Use Affinity tools to help users "
        "with their requests. Ask clarifying questions when needed."
    ),
)
What's happening:
  • The MCP client connects to the Affinity endpoint
  • The agent uses GPT-5 to interpret user commands and perform Affinity 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 Affinity.\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
  • Affinity 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 Affinity 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 Affinity
    composio = Composio(api_key=api_key)
    session = composio.create(
        user_id=user_id,
        toolkits=["affinity"],
    )
    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
    affinity_mcp = MCPServerStreamableHTTP(url, headers={"x-api-key": COMPOSIO_API_KEY})
    agent = Agent(
        "openai:gpt-5",
        toolsets=[affinity_mcp],
        instructions=(
            "You are a Affinity assistant. Use Affinity 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 Affinity.\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 Affinity through Composio's Tool Router. With this setup, your agent can perform real Affinity 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 + Affinity 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 Affinity MCP Agent with another framework

OpenAI Agents SDK

OpenAI Agents SDK

Use Affinity MCP with OpenAI Agents SDK

Claude Agent SDK

Claude Agent SDK

Use Affinity MCP with Claude Agent SDK

Google ADK

Google ADK

Use Affinity MCP with Google ADK

LangChain

LangChain

Use Affinity MCP with LangChain

Vercel AI SDK

Vercel AI SDK

Use Affinity MCP with Vercel AI SDK

Mastra AI

Mastra AI

Use Affinity MCP with Mastra AI

LlamaIndex

LlamaIndex

Use Affinity MCP with LlamaIndex

CrewAI

CrewAI

Use Affinity MCP with CrewAI

Claude Code

Claude Code

Use Affinity MCP with Claude Code

FAQ

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

With a standalone Affinity MCP server, the agents and LLMs can only access a fixed set of Affinity tools tied to that server. However, with the Composio Tool Router, agents can dynamically load tools from Affinity 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 Affinity tools.

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

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

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