Download OpenAPI specification:
Private API for accessing cross-market arbitrage opportunities between prediction-market venues (currently Kalshi and Polymarket).
Send your API key in the X-API-Key request header:
X-API-Key: private_key_here
or
Authorization: Bearer private_key_here
The /api/demo-opportunities endpoint is public and needs no key.
Each opportunity is venue-agnostic: it carries a legs array describing the
trades that, executed together, lock in the profit. Each leg names the
venue, the side you buy there (yes/no), and its price.
Returns the current arbitrage opportunities (priced for 100 shares). Requires a valid API key.
{- "status": "success",
- "shares": 100,
- "length": 1,
- "last_updated": "2025-10-31T13:18:20+00:00",
- "items": [
- {
- "outcome": "Spain",
- "profit": 1.6,
- "legs": [
- {
- "venue": "polymarket",
- "side": "yes",
- "price": 15.4,
- "title": "Will Spain win the 2026 FIFA World Cup?",
- "end_date": "2026-07-20T00:00:00+00:00"
}, - {
- "venue": "kalshi",
- "side": "no",
- "price": 83,
- "title": "2026 Men's World Cup winner?",
- "end_date": "2026-07-19T14:00:00+00:00"
}
]
}
]
}A public, unauthenticated endpoint returning up to two opportunities. No API key required.
{- "status": "success",
- "shares": 100,
- "length": 1,
- "last_updated": "2025-10-31T13:18:20+00:00",
- "items": [
- {
- "outcome": "Spain",
- "profit": 1.6,
- "legs": [
- {
- "venue": "polymarket",
- "side": "yes",
- "price": 15.4,
- "title": "Will Spain win the 2026 FIFA World Cup?",
- "end_date": "2026-07-20T00:00:00+00:00"
}, - {
- "venue": "kalshi",
- "side": "no",
- "price": 83,
- "title": "2026 Men's World Cup winner?",
- "end_date": "2026-07-19T14:00:00+00:00"
}
]
}
]
}