prediction-market-sdk

TypeScript SDK for the Prediction Market Data API — unified access to Polymarket & Kalshi markets, arbitrage detection, cross-platform matching, and strategy signals.

Since Dome (the previous prediction market aggregator) was acquired by Polymarket in early 2026, there is no unified API for both major prediction market platforms. This SDK fills that gap.

Install

npm install prediction-market-sdk

Quick Start

import { PredictionMarketClient } from "prediction-market-sdk";

const client = new PredictionMarketClient({
  apiKey: "your-rapidapi-key",
});

// Search markets
const markets = await client.listMarkets({
  category: "Sports",
  platform: "polymarket",
  limit: 10,
});

// Find arbitrage opportunities
const arbs = await client.getArbitrage({ minSpread: 0.02 });

// Cross-platform arbitrage (same event, different prices)
const crossArbs = await client.getCrossPlatformArbitrage({ arbOnly: true });

// Strategy signals from 759K+ forward-tested triggers
const strategies = await client.getTopStrategies({ minWinRate: 0.8 });

Get an API Key

1. Go to Prediction Market Data on RapidAPI
2. Subscribe to the free plan (50 requests/day)
3. Copy your X-RapidAPI-Key from the dashboard

API Methods

Markets

listMarkets(params?)

List active prediction markets from Polymarket and Kalshi, sorted by 24h volume.

const markets = await client.listMarkets({
  platform: "polymarket",  // or "kalshi"
  category: "Politics",
  q: "Trump",              // search by question text
  minVolume: 10000,
  limit: 50,
  offset: 0,
});

getMarket(id)

Get a single market by Polymarket conditionId (0x...) or Kalshi ticker.

const market = await client.getMarket("0xe492ad95...");

listCategories()

List all categories with per-platform market counts.

const categories = await client.listCategories();
// [{ name: "Sports", polymarketCount: 824, kalshiCount: 612, totalCount: 1436 }, ...]

Arbitrage

getArbitrage(params?)

Find single-platform arbitrage opportunities where YES + NO < $1.

const arbs = await client.getArbitrage({
  platform: "kalshi",
  minSpread: 0.01,
  shares: 100,
  limit: 20,
});

getCrossPlatformArbitrage(params?)

Find the same market priced differently on Polymarket vs Kalshi. Uses NLP-powered matching with question type detection, entity extraction, and predicate analysis.

const crossArbs = await client.getCrossPlatformArbitrage({
  minMatchScore: 0.7, // 0-1 confidence threshold
  arbOnly: true,      // only profitable opportunities
  limit: 50,
});

for (const match of crossArbs.data) {
  console.log(`${match.polymarket.question} — ${match.matchScore * 100}% match`);
  console.log(`Buy YES on ${match.bestStrategy.buyYesOn} → ROI: ${match.bestStrategy.roi}%`);
}

calculateArbitrage(params)

Calculate exact profit for a YES/NO price pair with platform-specific fee breakdown.

const calc = await client.calculateArbitrage({
  yes: 0.45,
  no: 0.52,
  shares: 100,
  platform: "polymarket",
  feeType: "us",
});
// { netProfit: 1.93, roi: 1.99, isProfitable: true, fees: { taker: 0.01, settlement: 1, ... } }

Signals

getTopStrategies(params?)

Top-performing strategy combinations from a 24/7 forward-testing engine evaluating 864 combos against live Polymarket data ~8,640 times per day.

const strategies = await client.getTopStrategies({
  minWinRate: 0.8,
  minTriggers: 1000,
  limit: 10,
});
// [{ comboId: 24, winRate: 0.8268, totalNetProfit: 286140, totalTriggers: 759253, ... }]

getRecentTriggers(params?)

Recent trigger events — each represents a real market opportunity detected and evaluated.

const triggers = await client.getRecentTriggers({
  profitable: true,
  category: "Sports",
  limit: 20,
});

Data Coverage

| Platform | Markets | Type | |----------|---------|------| | Polymarket | ~1,400+ | Crypto-native, largest by volume | | Kalshi | ~3,400+ | CFTC-regulated US exchange |

Pricing

| Plan | Price | Requests | |------|-------|----------| | Basic | Free | 50/day | | Pro | $14.99/mo | 1,000/day | | Ultra | $49.99/mo | 10,000/day | | Mega | $149.99/mo | 100,000/mo |

Subscribe on RapidAPI →

License

MIT