How to integrate Polymarket US MCP with OpenAI Agents SDK

This guide walks you through connecting Polymarket US to the OpenAI Agents SDK 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 OpenAI Agents SDK 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.

Polymarket US logoPolymarket 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.

44 Tools

Introduction

This guide walks you through connecting Polymarket US to the OpenAI Agents SDK 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 OpenAI Agents SDK 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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TL;DR

Here's what you'll learn:
  • Get and set up your OpenAI and Composio API keys
  • Install the necessary dependencies
  • Initialize Composio and create a Tool Router session for Polymarket US
  • Configure an AI agent that can use Polymarket US as a tool
  • Run a live chat session where you can ask the agent to perform Polymarket US operations

What is OpenAI Agents SDK?

The OpenAI Agents SDK is a lightweight framework for building AI agents that can use tools and maintain conversation state. It provides a simple interface for creating agents with hosted MCP tool support.

Key features include:

  • Hosted MCP Tools: Connect to external services through hosted MCP endpoints
  • SQLite Sessions: Persist conversation history across interactions
  • Simple API: Clean interface with Agent, Runner, and tool configuration
  • Streaming Support: Real-time response streaming for interactive applications

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:

  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:
  • Composio API Key and OpenAI API Key
  • Primary know-how of OpenAI Agents SDK
  • A live Polymarket US project
  • Some knowledge of Python or Typescript
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
3

Install dependencies

npm install @composio/openai-agents @openai/agents dotenv

Install the Composio SDK and the OpenAI Agents SDK.

4

Set up environment variables

bash
OPENAI_API_KEY=sk-...your-api-key
COMPOSIO_API_KEY=your-api-key
USER_ID=composio_user@gmail.com

Create a .env file and add your OpenAI and Composio API keys.

5

Import dependencies

import 'dotenv/config';
import { Composio } from '@composio/core';
import { OpenAIAgentsProvider } from '@composio/openai-agents';
import { Agent, hostedMcpTool, run, OpenAIConversationsSession } from '@openai/agents';
import * as readline from 'readline';
What's happening:
  • You're importing all necessary libraries.
  • The Composio and OpenAIAgentsProvider classes are imported to connect your OpenAI agent to Composio tools like Polymarket US.
6

Set up the Composio instance

dotenv.config();

const composioApiKey = process.env.COMPOSIO_API_KEY;
const userId = process.env.USER_ID;

if (!composioApiKey) {
  throw new Error('COMPOSIO_API_KEY is not set. Create a .env file with COMPOSIO_API_KEY=your_key');
}
if (!userId) {
  throw new Error('USER_ID is not set');
}

// Initialize Composio
const composio = new Composio({
  apiKey: composioApiKey,
  provider: new OpenAIAgentsProvider(),
});
What's happening:
  • dotenv.config() loads your .env file so COMPOSIO_API_KEY and USER_ID are available as environment variables.
  • Creating a Composio instance using the API Key and OpenAIAgentsProvider class.
7

Create a Tool Router session

// Create Tool Router session for Polymarket US
const session = await composio.create(userId as string, {
  toolkits: ['polymarket_us'],
});
const mcpUrl = session.mcp.url;

What is happening:

  • You give the Tool Router the user id and the toolkits you want available. Here, it is only polymarket_us.
  • The router checks the user's Polymarket US connection and prepares the MCP endpoint.
  • The returned session.mcp.url is the MCP URL that your agent will use to access Polymarket US.
  • This approach keeps things lightweight and lets the agent request Polymarket US tools only when needed during the conversation.
8

Configure the agent

// Configure agent with MCP tool
const agent = new Agent({
  name: 'Assistant',
  model: 'gpt-5',
  instructions:
    'You are a helpful assistant that can access Polymarket US. Help users perform Polymarket US operations through natural language.',
  tools: [
    hostedMcpTool({
      serverLabel: 'tool_router',
      serverUrl: mcpUrl,
      headers: { 'x-api-key': composioApiKey },
      requireApproval: 'never',
    }),
  ],
});
What's happening:
  • We're creating an Agent instance with a name, model (gpt-5), and clear instructions about its purpose.
  • The agent's instructions tell it that it can access Polymarket US and help with queries, inserts, updates, authentication, and fetching database information.
  • The tools array includes a hostedMcpTool that connects to the MCP server URL we created earlier.
  • The headers object includes the Composio API key for secure authentication with the MCP server.
  • requireApproval: 'never' means the agent can execute Polymarket US operations without asking for permission each time, making interactions smoother.
9

Start chat loop and handle conversation

// Keep conversation state across turns
const conversationSession = new OpenAIConversationsSession();

// Simple CLI
const rl = readline.createInterface({
  input: process.stdin,
  output: process.stdout,
  prompt: 'You: ',
});

console.log('\nComposio Tool Router session created.');
console.log('\nChat started. Type your requests below.');
console.log("Commands: 'exit', 'quit', or 'q' to end\n");

try {
  const first = await run(agent, 'What can you help me with?', { session: conversationSession });
  console.log(`Assistant: ${first.finalOutput}\n`);
} catch (e) {
  console.error('Error:', e instanceof Error ? e.message : e, '\n');
}

rl.prompt();

rl.on('line', async (userInput) => {
  const text = userInput.trim();

  if (['exit', 'quit', 'q'].includes(text.toLowerCase())) {
    console.log('Goodbye!');
    rl.close();
    process.exit(0);
  }

  if (!text) {
    rl.prompt();
    return;
  }

  try {
    const result = await run(agent, text, { session: conversationSession });
    console.log(`\nAssistant: ${result.finalOutput}\n`);
  } catch (e) {
    console.error('Error:', e instanceof Error ? e.message : e, '\n');
  }

  rl.prompt();
});

rl.on('close', () => {
  console.log('\n👋 Session ended.');
  process.exit(0);
});
What's happening:
  • The program prints a session URL that you visit to authorize Polymarket US.
  • After authorization, the chat begins.
  • Each message you type is processed by the agent using run().
  • The responses are printed to the console.
  • Typing exit, quit, or q cleanly ends the chat.

Complete Code

Here's the complete code to get you started with Polymarket US and OpenAI Agents SDK:

import 'dotenv/config';
import { Composio } from '@composio/core';
import { OpenAIAgentsProvider } from '@composio/openai-agents';
import { Agent, hostedMcpTool, run, OpenAIConversationsSession } from '@openai/agents';
import * as readline from 'readline';

const composioApiKey = process.env.COMPOSIO_API_KEY;
const userId = process.env.USER_ID;

if (!composioApiKey) {
  throw new Error('COMPOSIO_API_KEY is not set. Create a .env file with COMPOSIO_API_KEY=your_key');
}
if (!userId) {
  throw new Error('USER_ID is not set');
}

// Initialize Composio
const composio = new Composio({
  apiKey: composioApiKey,
  provider: new OpenAIAgentsProvider(),
});

async function main() {
  // Create Tool Router session
  const session = await composio.create(userId as string, {
    toolkits: ['polymarket_us'],
  });
  const mcpUrl = session.mcp.url;

  // Configure agent with MCP tool
  const agent = new Agent({
    name: 'Assistant',
    model: 'gpt-5',
    instructions:
      'You are a helpful assistant that can access Polymarket US. Help users perform Polymarket US operations through natural language.',
    tools: [
      hostedMcpTool({
        serverLabel: 'tool_router',
        serverUrl: mcpUrl,
        headers: { 'x-api-key': composioApiKey },
        requireApproval: 'never',
      }),
    ],
  });

  // Keep conversation state across turns
  const conversationSession = new OpenAIConversationsSession();

  // Simple CLI
  const rl = readline.createInterface({
    input: process.stdin,
    output: process.stdout,
    prompt: 'You: ',
  });

  console.log('\nComposio Tool Router session created.');
  console.log('\nChat started. Type your requests below.');
  console.log("Commands: 'exit', 'quit', or 'q' to end\n");

  try {
    const first = await run(agent, 'What can you help me with?', { session: conversationSession });
    console.log(`Assistant: ${first.finalOutput}\n`);
  } catch (e) {
    console.error('Error:', e instanceof Error ? e.message : e, '\n');
  }

  rl.prompt();

  rl.on('line', async (userInput) => {
    const text = userInput.trim();

    if (['exit', 'quit', 'q'].includes(text.toLowerCase())) {
      console.log('Goodbye!');
      rl.close();
      process.exit(0);
    }

    if (!text) {
      rl.prompt();
      return;
    }

    try {
      const result = await run(agent, text, { session: conversationSession });
      console.log(`\nAssistant: ${result.finalOutput}\n`);
    } catch (e) {
      console.error('Error:', e instanceof Error ? e.message : e, '\n');
    }

    rl.prompt();
  });

  rl.on('close', () => {
    console.log('\nSession ended.');
    process.exit(0);
  });
}

main().catch((err) => {
  console.error('Fatal error:', err);
  process.exit(1);
});

Conclusion

This was a starter code for integrating Polymarket US MCP with OpenAI Agents SDK to build a functional AI agent that can interact with Polymarket US.

Key features:

  • Hosted MCP tool integration through Composio's Tool Router
  • SQLite session persistence for conversation history
  • Simple async chat loop for interactive testing
You can extend this by adding more toolkits, implementing custom business logic, or building a web interface around the agent.
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.

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. OpenAI Agents SDK 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.

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