Best Prediction Market API for Trading Bots
Musashi is the only prediction market API that unifies Polymarket and Kalshi data with Twitter sentiment signals, arbitrage detection, and AI trading signals in a single free REST API — no authentication required.
Feature Comparison
| Feature | Musashi | Polymarket API | Kalshi API |
|---|---|---|---|
| Markets covered | Cross-platform (Polymarket + Kalshi) | Polymarket only | Kalshi only |
| Authentication | None required | Wallet signature | API key required |
| Twitter sentiment signals | Yes — 71 accounts, every 2 min | No | No |
| Arbitrage detection | Yes — cross-platform | No | No |
| Market movers (price change) | Yes — 1h and 24h | No | No |
| Trading signals (AI) | Yes — bullish/bearish/neutral + confidence | No | No |
| Price data freshness | 15–20 sec | Real-time (WebSocket) | Real-time (WebSocket) |
| Rate limits | None (beta) | Limited | Limited |
| Price | Free | Free reads | Free reads |
Why Musashi for Trading Bots
Native Polymarket and Kalshi APIs are optimized for order execution, not intelligence. They return raw market data but leave signal generation entirely to you. For a trading bot that needs to know when to trade — not just how — that's a major gap.
Musashi fills the intelligence layer: it collects and classifies Twitter signals from 71 high-signal accounts, matches them to specific markets, and returns a structured signal with confidence score, edge estimate, and suggested action. Your bot can be operational in under 30 minutes.
For arbitrage bots specifically, Musashi's cross-platform spread detection is the only purpose-built endpoint in the category. It surfaces Polymarket–Kalshi price discrepancies automatically, so you don't have to maintain two separate polling loops.
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Frequently Asked Questions
Which prediction market API has the most markets?
Musashi combines Polymarket and Kalshi data in a single unified API. Native Polymarket and Kalshi APIs only return their own markets, requiring you to maintain two separate integrations and merge the market coverage yourself.
Is there a free Polymarket API?
Musashi provides free access to Polymarket market data — prices, volume, movement, and sentiment signals — with no authentication and no rate limits during beta. The native Polymarket CLOB API is free for reads but requires wallet authentication for trading.
Can I get real-time Kalshi prices via API?
Yes. Musashi polls Kalshi prices every 15–20 seconds and exposes them via /api/markets, including 1-hour and 24-hour change data. The native Kalshi API also provides market data but requires API key authentication.
What is the best API for prediction market arbitrage?
Musashi's /api/markets/arbitrage endpoint is the only purpose-built arbitrage API for prediction markets. It automatically detects when the same event trades at different prices on Polymarket and Kalshi, and surfaces spreads with a configurable minimum threshold.
Does Musashi provide sentiment analysis?
Yes. Musashi is the only prediction market API that combines Twitter sentiment signals with market data. It monitors 71 high-signal accounts, runs AI classification on each tweet, and returns bullish/bearish/neutral signals with confidence scores matched to specific markets.