How to integrate Polymarket US MCP with Pydantic AI

This guide walks you through connecting Polymarket US to Pydantic AI using the Composio tool router. By the end, you'll have a working Polymarket US agent that can list active polymarket us election markets, show your polymarket us open positions, check polymarket us market order books through natural language commands. This guide will help you understand how to give your Pydantic AI agent real control over a Polymarket US account through Composio's Polymarket US MCP server. Before we dive in, let's take a quick look at the key ideas and tools involved.

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Polymarket US

Api Key

Polymarket US is the CFTC-compliant Polymarket product for verified United States users. Use it to access regulated prediction market data and account workflows through official API credentials.

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Introduction

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

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

Also integrate Polymarket US with

OpenAI Agents SDK Claude Agent SDK Claude Code Claude Cowork Codex OpenClaw Hermes CLI Google ADK LangChain Vercel AI SDK Mastra AI LlamaIndex CrewAI

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 Polymarket US
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 Polymarket US 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 Polymarket US MCP server, and what's possible with it?

The Polymarket US MCP server is an implementation of the Model Context Protocol that connects your AI agent and assistants like Claude, Cursor, etc directly to your Polymarket US account. It provides structured and secure access to your markets, orders, balances, positions, and activity, so your agent can discover markets, inspect prices, place or cancel orders, and monitor your portfolio on your behalf.

Market and event discovery: Have your agent find Polymarket US markets, events, subjects, series, and featured topics that match your interests.
Price and order book research: Let the agent check the best bid and offer, review market order books, inspect market details, and look up settlement information.
Order creation and management: Direct your agent to place one or several live orders, review open orders, close a position, or cancel selected or all open orders.
Portfolio monitoring: Instruct your agent to check account balances, review current positions, and summarize trades, deposits, withdrawals, resolutions, bonuses, and transfers.
Sports market exploration: Have your agent browse sports, leagues, teams, and related events, including markets for leagues such as the NBA or NFL.

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:

Discovery: Searches for tools matching your task and returns relevant toolkits with their details.
Authentication: Checks for active connections. If missing, creates an auth config and returns a connection URL via Auth Link.
Execution: Executes the action using the authenticated connection.

Step-by-step Guide

Step by step09 STEPS

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 Polymarket US
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 Polymarket US
MCPServerStreamableHTTP connects to the Polymarket US 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 Polymarket US
    composio = Composio(api_key=api_key)
    session = composio.create(
        user_id=user_id,
        toolkits=["polymarket_us"],
    )
    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 Polymarket US 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
polymarket_us_mcp = MCPServerStreamableHTTP(url, headers={"x-api-key": COMPOSIO_API_KEY})
agent = Agent(
    "openai:gpt-5",
    toolsets=[polymarket_us_mcp],
    instructions=(
        "You are a Polymarket US assistant. Use Polymarket US tools to help users "
        "with their requests. Ask clarifying questions when needed."
    ),
)

What's happening:

The MCP client connects to the Polymarket US endpoint
The agent uses GPT-5 to interpret user commands and perform Polymarket US 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 Polymarket US.\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
Polymarket US 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 Polymarket US 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 Polymarket US
    composio = Composio(api_key=api_key)
    session = composio.create(
        user_id=user_id,
        toolkits=["polymarket_us"],
    )
    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
    polymarket_us_mcp = MCPServerStreamableHTTP(url, headers={"x-api-key": COMPOSIO_API_KEY})
    agent = Agent(
        "openai:gpt-5",
        toolsets=[polymarket_us_mcp],
        instructions=(
            "You are a Polymarket US assistant. Use Polymarket US 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 Polymarket US.\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 Polymarket US through Composio's Tool Router. With this setup, your agent can perform real Polymarket US 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 + Polymarket US 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 Polymarket US action and event your agent gets out of the box.

Cancel All Open Orders

Cancel all authenticated Polymarket US open orders, optionally scoped to specific market slugs.

Cancel Multiple Orders

Cancel up to 20 Polymarket US open orders in one request.

Cancel Order

Cancel one Polymarket US open order by exchange-assigned order ID.

Close Position Order

Create a live Polymarket US order intended to close an existing position in one market.

Create Multiple Orders

Submit up to 20 live Polymarket US orders in one request.

Create Order

Submit one live Polymarket US order.

Get Account Balances

Get the authenticated user's Polymarket US account balances.

Get Activities

Get authenticated Polymarket US portfolio activities such as trades, resolutions, deposits, withdrawals, referral bonuses, and transfers.

Get Event By ID

Get one Polymarket US event by numeric ID from the public gateway API.

Get Event By Slug

Get one Polymarket US event by slug from the public gateway API.

Get League By Slug

Get a current Polymarket US v2 league by slug.

Get Market BBO

Get the best bid and offer for one Polymarket US market by slug.

Get Market Book

Get the public order book for one Polymarket US market by slug.

Get Market By ID

Get one Polymarket US market by numeric ID from the public gateway API.

Get Market By Slug

Get one Polymarket US market by slug from the public gateway API.

Get Market Settlement

Get settlement information for one Polymarket US market by slug.

Get Markets For Subject

Discover Polymarket US markets associated with a subject ID.

Get Markets For Subject By Slug

Discover Polymarket US markets associated with a subject slug.

Get Open Orders

Get all open orders for the authenticated Polymarket US user.

Get Order

Get an authenticated user's Polymarket US order by exchange-assigned order ID.

Get Series By ID

Get a Polymarket US series by numeric ID.

Get Sport By Slug

Get a current Polymarket US v2 sport by slug.

Get Subject By ID

Get a Polymarket US subject entity by numeric ID.

Get Subject By Slug

Get a Polymarket US subject entity by slug.

Get Tag By ID

Get a Polymarket US topic, sport, or league tag by numeric ID.

Get Tag By Slug

Get a Polymarket US topic, sport, or league tag by slug.

Get User Positions

Get the authenticated user's Polymarket US trading positions across all markets or filtered by a specific market slug.

List Events

Discover Polymarket US events from the public gateway API.

List Events For League

List Polymarket US events for a current v2 league slug such as "nba" or "nfl".

List Events For Series

List Polymarket US sports events for a legacy v1 series ID.

List Events For Sport

List Polymarket US events for a current v2 sport slug such as "football" or "basketball".

List Featured Tags

List featured Polymarket US tag sections from the public gateway API.

List Leagues

List current Polymarket US sports leagues from the v2 public gateway API.

List Markets

Discover Polymarket US markets from the public gateway API.

List Series

List Polymarket US series from the public gateway API.

List Sports

List Polymarket US sports from the current v2 public gateway API.

List Sports Teams

List Polymarket US sports teams from the legacy v1 public gateway API.

List Sports Teams For Provider

List Polymarket US legacy v1 sports team mappings for a data provider.

List Subjects

List Polymarket US subject entities from the public gateway API.

List Tags

List ranked Polymarket US tags from the public gateway API.

Modify Multiple Orders

Modify up to 20 Polymarket US open orders in one request.

Modify Order

Modify one existing Polymarket US open order.

Preview Order

Preview a Polymarket US order without submitting it to the market.

Search Markets And Events

Search public Polymarket US markets and events for discovery.

FRAMEWORKS

How to build Polymarket US MCP Agent with another framework

OpenAI Agents SDK

Use Polymarket US MCP with OpenAI Agents SDK

Claude Agent SDK

Use Polymarket US MCP with Claude Agent SDK

Claude Code

Use Polymarket US MCP with Claude Code

Claude Cowork

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Codex

Use Polymarket US MCP with Codex

OpenClaw

Use Polymarket US MCP with OpenClaw

Hermes

Use Polymarket US MCP with Hermes

CLI

Use Polymarket US MCP with CLI

Google ADK

Use Polymarket US MCP with Google ADK

LangChain

Use Polymarket US MCP with LangChain

Vercel AI SDK

Use Polymarket US MCP with Vercel AI SDK

Mastra AI

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LlamaIndex

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CrewAI

Use Polymarket US MCP with CrewAI

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FAQ

Frequently asked questions

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

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

Start with Polymarket US.It takes 30 seconds.

Managed auth, hosted MCP servers, and every Polymarket US tool your agent needs.Free to start.

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Customer stories

Teams ship real agents on Composio

GET STARTED FOR FREE BOOK A DEMO

Karan skipped his own birthday party to fix our critical issue. It was 10pm and he diverted his Waymo to help us instead. This really sets the bar — it shows the commitment you need when users rely on your software.

Harsha Gaddipati

Co-founder, Slashy

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.

Abhi Arya

Co-founder, Opennote

We chose Composio over Pipedream because it delivered depth where it mattered — niche tools and tricky edge cases other platforms simply ignored. That gave us confidence to scale without compromising.

Nirman Dave

CEO, Zams

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.

Ryan Yu

Founder, Extra Thursday

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.

Tomisin Jenrola

Founder & CEO, SwarmZero

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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How to integrate Polymarket US MCP with Pydantic AI

Connect Polymarket US without auth hassles

Introduction

Also integrate Polymarket US with

TL;DR

What is Pydantic AI?

What is the Polymarket US MCP server, and what's possible with it?

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

What is Composio SDK?

How the Composio SDK works

Step-by-step Guide

Prerequisites

Getting API Keys for OpenAI and Composio

Install dependencies

Set up environment variables

Import dependencies

Create a Tool Router Session

Initialize the Pydantic AI Agent

Build the chat interface

Run the application

Complete Code

Conclusion

Supported Tools

How to build Polymarket US MCP Agent with another framework

OpenAI Agents SDK

Claude Agent SDK

Claude Code

Claude Cowork

Codex

OpenClaw

Hermes

CLI

Google ADK

LangChain

Vercel AI SDK

Mastra AI

LlamaIndex

CrewAI

Explore Other Toolkits

44API

Alpaca

Billsby

Brex

Frequently asked questions

What are the differences in Tool Router MCP and Polymarket US MCP?+

Can I use Tool Router MCP with Pydantic AI?+

Can I manage the permissions and scopes for Polymarket US while using Tool Router?+

How safe is my data with Composio Tool Router?+

Start with Polymarket US.It takes 30 seconds.

Teams ship real agents on Composio