How to integrate Polymarket US MCP with Mastra AI

This guide walks you through connecting Polymarket US to Mastra 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 Mastra 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 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 Mastra 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 Mastra 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 SDKClaude Agent SDKClaude CodeClaude CoworkCodexOpenClawHermesCLIGoogle ADKLangChainVercel AI SDKLlamaIndexCrewAI

TL;DR

Here's what you'll learn:
  • Set up your environment so Mastra, OpenAI, and Composio work together
  • Create a Tool Router session in Composio that exposes Polymarket US tools
  • Connect Mastra's MCP client to the Composio generated MCP URL
  • Fetch Polymarket US tool definitions and attach them as a toolset
  • Build a Mastra agent that can reason, call tools, and return structured results
  • Run an interactive CLI where you can chat with your Polymarket US agent

What is Mastra AI?

Mastra AI is a TypeScript framework for building AI agents with tool support. It provides a clean API for creating agents that can use external services through MCP.

Key features include:

  • MCP Client: Built-in support for Model Context Protocol servers
  • Toolsets: Organize tools into logical groups
  • Step Callbacks: Monitor and debug agent execution
  • OpenAI Integration: Works with OpenAI models via @ai-sdk/openai

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:
  • Node.js 18 or higher
  • A Composio account with an active API key
  • An OpenAI API key
  • Basic familiarity with TypeScript
2

Getting API Keys for OpenAI and Composio

OpenAI API Key
  • Go to the OpenAI dashboard and create an API key.
  • You need credits or a connected billing setup to use the models.
  • Store the key somewhere safe.
Composio API Key
  • Log in to the Composio dashboard.
  • Go to Settings and copy your API key.
  • This key lets your Mastra agent talk to Composio and reach Polymarket US through MCP.
3

Install dependencies

bash
npm install @composio/core @mastra/core @mastra/mcp @ai-sdk/openai dotenv

Install the required packages.

What's happening:

  • @composio/core is the Composio SDK for creating MCP sessions
  • @mastra/core provides the Agent class
  • @mastra/mcp is Mastra's MCP client
  • @ai-sdk/openai is the model wrapper for OpenAI
  • dotenv loads environment variables from .env
4

Set up environment variables

bash
COMPOSIO_API_KEY=your_composio_api_key_here
COMPOSIO_USER_ID=your_user_id_here
OPENAI_API_KEY=your_openai_api_key_here

Create a .env file in your project root.

What's happening:

  • COMPOSIO_API_KEY authenticates your requests to Composio
  • COMPOSIO_USER_ID tells Composio which user this session belongs to
  • OPENAI_API_KEY lets the Mastra agent call OpenAI models
5

Import libraries and validate environment

typescript
import "dotenv/config";
import { openai } from "@ai-sdk/openai";
import { Agent } from "@mastra/core/agent";
import { MCPClient } from "@mastra/mcp";
import { Composio } from "@composio/core";
import * as readline from "readline";

import type { AiMessageType } from "@mastra/core/agent";

const openaiAPIKey = process.env.OPENAI_API_KEY;
const composioAPIKey = process.env.COMPOSIO_API_KEY;
const composioUserID = process.env.COMPOSIO_USER_ID;

if (!openaiAPIKey) throw new Error("OPENAI_API_KEY is not set");
if (!composioAPIKey) throw new Error("COMPOSIO_API_KEY is not set");
if (!composioUserID) throw new Error("COMPOSIO_USER_ID is not set");

const composio = new Composio({
  apiKey: composioAPIKey as string,
});
What's happening:
  • dotenv/config auto loads your .env so process.env.* is available
  • openai gives you a Mastra compatible model wrapper
  • Agent is the Mastra agent that will call tools and produce answers
  • MCPClient connects Mastra to your Composio MCP server
  • Composio is used to create a Tool Router session
6

Create a Tool Router session for Polymarket US

typescript
async function main() {
  const session = await composio.create(
    composioUserID as string,
    {
      toolkits: ["polymarket_us"],
    },
  );

  const composioMCPUrl = session.mcp.url;
  console.log("Polymarket US MCP URL:", composioMCPUrl);
What's happening:
  • create spins up a short-lived MCP HTTP endpoint for this user
  • The toolkits array contains "polymarket_us" for Polymarket US access
  • session.mcp.url is the MCP URL that Mastra's MCPClient will connect to
7

Configure Mastra MCP client and fetch tools

typescript
const mcpClient = new MCPClient({
    id: composioUserID as string,
    servers: {
      nasdaq: {
        url: new URL(composioMCPUrl),
        requestInit: {
          headers: session.mcp.headers,
        },
      },
    },
    timeout: 30_000,
  });

console.log("Fetching MCP tools from Composio...");
const composioTools = await mcpClient.getTools();
console.log("Number of tools:", Object.keys(composioTools).length);
What's happening:
  • MCPClient takes an id for this client and a list of MCP servers
  • The headers property includes the x-api-key for authentication
  • getTools fetches the tool definitions exposed by the Polymarket US toolkit
8

Create the Mastra agent

typescript
const agent = new Agent({
    name: "polymarket_us-mastra-agent",
    instructions: "You are an AI agent with Polymarket US tools via Composio.",
    model: "openai/gpt-5",
  });
What's happening:
  • Agent is the core Mastra agent
  • name is just an identifier for logging and debugging
  • instructions guide the agent to use tools instead of only answering in natural language
  • model uses openai("gpt-5") to configure the underlying LLM
9

Set up interactive chat interface

typescript
let messages: AiMessageType[] = [];

console.log("Chat started! Type 'exit' or 'quit' to end.\n");

const rl = readline.createInterface({
  input: process.stdin,
  output: process.stdout,
  prompt: "> ",
});

rl.prompt();

rl.on("line", async (userInput: string) => {
  const trimmedInput = userInput.trim();

  if (["exit", "quit", "bye"].includes(trimmedInput.toLowerCase())) {
    console.log("\nGoodbye!");
    rl.close();
    process.exit(0);
  }

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

  messages.push({
    id: crypto.randomUUID(),
    role: "user",
    content: trimmedInput,
  });

  console.log("\nAgent is thinking...\n");

  try {
    const response = await agent.generate(messages, {
      toolsets: {
        polymarket_us: composioTools,
      },
      maxSteps: 8,
    });

    const { text } = response;

    if (text && text.trim().length > 0) {
      console.log(`Agent: ${text}\n`);
        messages.push({
          id: crypto.randomUUID(),
          role: "assistant",
          content: text,
        });
      }
    } catch (error) {
      console.error("\nError:", error);
    }

    rl.prompt();
  });

  rl.on("close", async () => {
    console.log("\nSession ended.");
    await mcpClient.disconnect();
    process.exit(0);
  });
}

main().catch((err) => {
  console.error("Fatal error:", err);
  process.exit(1);
});
What's happening:
  • messages keeps the full conversation history in Mastra's expected format
  • agent.generate runs the agent with conversation history and Polymarket US toolsets
  • maxSteps limits how many tool calls the agent can take in a single run
  • onStepFinish is a hook that prints intermediate steps for debugging

Complete Code

Here's the complete code to get you started with Polymarket US and Mastra AI:

typescript
import "dotenv/config";
import { openai } from "@ai-sdk/openai";
import { Agent } from "@mastra/core/agent";
import { MCPClient } from "@mastra/mcp";
import { Composio } from "@composio/core";
import * as readline from "readline";

import type { AiMessageType } from "@mastra/core/agent";

const openaiAPIKey = process.env.OPENAI_API_KEY;
const composioAPIKey = process.env.COMPOSIO_API_KEY;
const composioUserID = process.env.COMPOSIO_USER_ID;

if (!openaiAPIKey) throw new Error("OPENAI_API_KEY is not set");
if (!composioAPIKey) throw new Error("COMPOSIO_API_KEY is not set");
if (!composioUserID) throw new Error("COMPOSIO_USER_ID is not set");

const composio = new Composio({ apiKey: composioAPIKey as string });

async function main() {
  const session = await composio.create(composioUserID as string, {
    toolkits: ["polymarket_us"],
  });

  const composioMCPUrl = session.mcp.url;

  const mcpClient = new MCPClient({
    id: composioUserID as string,
    servers: {
      polymarket_us: {
        url: new URL(composioMCPUrl),
        requestInit: {
          headers: session.mcp.headers,
        },
      },
    },
    timeout: 30_000,
  });

  const composioTools = await mcpClient.getTools();

  const agent = new Agent({
    name: "polymarket_us-mastra-agent",
    instructions: "You are an AI agent with Polymarket US tools via Composio.",
    model: "openai/gpt-5",
  });

  let messages: AiMessageType[] = [];

  const rl = readline.createInterface({
    input: process.stdin,
    output: process.stdout,
    prompt: "> ",
  });

  rl.prompt();

  rl.on("line", async (input: string) => {
    const trimmed = input.trim();
    if (["exit", "quit"].includes(trimmed.toLowerCase())) {
      rl.close();
      return;
    }

    messages.push({ id: crypto.randomUUID(), role: "user", content: trimmed });

    const { text } = await agent.generate(messages, {
      toolsets: { polymarket_us: composioTools },
      maxSteps: 8,
    });

    if (text) {
      console.log(`Agent: ${text}\n`);
      messages.push({ id: crypto.randomUUID(), role: "assistant", content: text });
    }

    rl.prompt();
  });

  rl.on("close", async () => {
    await mcpClient.disconnect();
    process.exit(0);
  });
}

main();

Conclusion

You've built a Mastra AI agent that can interact with Polymarket US through Composio's Tool Router. You can extend this further by:
  • Adding other toolkits like Gmail, Slack, or GitHub
  • Building a web-based chat interface around this agent
  • Using multiple MCP endpoints to enable cross-app workflows
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

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Claude Code

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Claude Cowork logo

Claude Cowork

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Codex logo

Codex

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OpenClaw logo

OpenClaw

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Hermes logo

Hermes

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CLI logo

CLI

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Google ADK logo

Google ADK

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LangChain logo

LangChain

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Vercel AI SDK logo

Vercel AI SDK

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LlamaIndex logo

LlamaIndex

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CrewAI logo

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. Mastra 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.

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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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