pmxtjs

A unified TypeScript/Node.js SDK for prediction markets — The ccxt for prediction markets.

Note: Use with a PMXT API key (hosted, recommended) or self-host the sidecar locally. Get a key at pmxt.dev/dashboard.

Installation

npm install pmxtjs

Quick Start

Get your API key at pmxt.dev/dashboard. For reads, only pmxtApiKey and walletAddress are required.

import { Polymarket } from "pmxtjs";

// Reads — pmxtApiKey + walletAddress only
const client = new Polymarket({
  pmxtApiKey: "pmxt_live_...",
  walletAddress: "0xYourWalletAddress",
});

// Search for markets
const markets = await client.fetchMarkets({ query: "Trump" });
console.log(markets[0].title);

// Get outcome details
const outcome = markets[0].outcomes[0];
console.log(`${outcome.label}: ${(outcome.price * 100).toFixed(1)}%`);

// Fetch historical data (use outcome.outcomeId!)
const candles = await client.fetchOHLCV(outcome.outcomeId, {
    resolution: '1d',
    limit: 30,
});

// Get current order book
const orderBook = await client.fetchOrderBook(outcome.outcomeId);
const spread = orderBook.asks[0].price - orderBook.bids[0].price;
console.log(`Spread: ${(spread * 100).toFixed(2)}%`);

// Account reads
const positions = await client.fetchPositions();
const balance = await client.fetchBalance();

How it works (hosted)

When you pass pmxtApiKey, the SDK talks to PMXT's hosted services: catalog requests go to api.pmxt.dev, trading requests go to trade.pmxt.dev. The SDK does not spawn a local process. For Polymarket and Opinion, PMXT's PreFundedEscrow handles custody — you sign orders with your own key, PMXT settles on-chain.

How it works (self-hosted)

Omit pmxtApiKey to use the local sidecar. Install pmxt-core from npm and supply venue credentials directly. See Self-hosted trading (advanced) below.

Core Methods

Market Data

• fetchMarkets(params?) - Get active markets

  // Fetch recent markets
  await poly.fetchMarkets({ limit: 20, sort: 'volume' });
  
  // Search by text
  await poly.fetchMarkets({ query: 'Fed rates', limit: 10 });
  
  // Fetch by slug/ticker
  await poly.fetchMarkets({ slug: 'who-will-trump-nominate-as-fed-chair' });

• fetchEvents(params?) - Get events (groups of related markets)

  await poly.fetchEvents({ query: 'Fed Chair', limit: 5 });

• filterMarkets(markets, query) - Filter markets by keyword

  const events = await poly.fetchEvents({ query: 'Fed Chair' });
  const warsh = poly.filterMarkets(events[0].markets, 'Kevin Warsh')[0];

Deep-Dive Methods

• fetchOHLCV(outcomeId, params) - Get historical price candles
• fetchOrderBook(outcomeId) - Get current bids/asks
• fetchTrades(outcomeId, params) - Get trade history

Helper Methods

• getExecutionPrice(orderBook, side, amount) - Calculate volume-weighted average price
• getExecutionPriceDetailed(orderBook, side, amount) - Get detailed execution info

Trading

Hosted trading (recommended)

With a PMXT API key, pass pmxtApiKey, walletAddress, and privateKey. The SDK auto-wraps your key into an EthersSigner and PMXT settles the order on-chain.

Polymarket:

import { Polymarket } from "pmxtjs";

const trader = new Polymarket({
  pmxtApiKey: "pmxt_live_...",
  walletAddress: "0xYourWalletAddress",
  privateKey: "0xYourPrivateKey",
});

const balance = await trader.fetchBalance();
console.log(`Available: $${balance[0].available}`);

const order = await trader.createOrder({
  marketId: "market-uuid",
  outcomeId: "outcome-uuid",
  side: "buy",
  type: "market",
  amount: 5.0,
  denom: "usdc",
  slippage_pct: 30.0,
} as any);
console.log(`Order status: ${order.status}`);

Opinion:

import { Opinion } from "pmxtjs";

const trader = new Opinion({
  pmxtApiKey: "pmxt_live_...",
  walletAddress: "0xYourWalletAddress",
  privateKey: "0xYourPrivateKey",
});

See the full hosted trading guide for venue support, custody model, and limits.

Self-hosted trading (advanced)

When self-hosting, supply venue credentials directly — no pmxtApiKey. The SDK spawns a local sidecar process.

Polymarket:

const poly = new pmxt.Polymarket({
    privateKey: process.env.POLYMARKET_PRIVATE_KEY,
    proxyAddress: process.env.POLYMARKET_PROXY_ADDRESS, // Optional
    // signatureType: 'gnosis-safe' (default)
});

Kalshi:

const kalshi = new pmxt.Kalshi({
    apiKey: process.env.KALSHI_API_KEY,
    privateKey: process.env.KALSHI_PRIVATE_KEY
});

Limitless:

const limitless = new pmxt.Limitless({
    privateKey: process.env.LIMITLESS_PRIVATE_KEY
});

Trading Methods

• createOrder(params) - Place a new order

  // Using outcome shorthand (recommended)
  await poly.createOrder({
      outcome: market.yes,
      side: 'buy',
      type: 'limit',
      amount: 10,
      price: 0.55
  });

• cancelOrder(orderId) - Cancel an open order

• fetchOrder(orderId) - Get order details

• fetchOpenOrders(marketId?) - Get all open orders

Account Methods

• fetchBalance() - Get account balance
• fetchPositions() - Get current positions

Documentation

For complete API documentation and examples, see:

• API Reference
• Examples
• Setup Guides

Important Notes

• Use outcome.outcomeId, not market.marketId for deep-dive methods (fetchOHLCV, fetchOrderBook, fetchTrades)
• Prices are 0.0 to 1.0 (multiply by 100 for percentages)
• Timestamps are Unix milliseconds
• Volumes are in USD

License

MIT