Prediction Market API for Kalshi, Polymarket and Sportsbook Odds
The GhostLeg Data API is a prediction market API and a sports odds API in one: a licensed layer over Kalshi, Polymarket and sportsbook prices that delivers processed intelligence rather than raw odds. Where most sports betting APIs return the price at a moment, this one returns composite signal scores, CLV analytics, sharp money consensus via Pinnacle, and three-way sportsbook vs. Kalshi vs. Polymarket divergence signals.
If you are looking for a Kalshi API or a Polymarket API to read those venues against the books, this is the comparison layer above both: Kalshi prediction market implied probabilities are tracked against sportsbook consensus in real time, and the Market Intelligence tier includes Polymarket divergence, which makes the signal three-way: sportsbooks, Kalshi and Polymarket on the same outcome.
Three tiers. gl_si_ Signal Intelligence: composite signal scores (0-100) across 7 components and win rates by score band, at 30 RPM, 1,000 requests a day and a 7-day lookback. gl_mi_ Market Intelligence: OCL, sharp consensus via Pinnacle, line velocity, steam moves, RLM and the book disagreement index across 7+ sportsbooks, at 60 RPM, 5,000 a day and a 90-day lookback. gl_ff_ Full Firehose: all signals, all sports, the full historical archive, at 120 RPM, 50,000 a day and a 730-day lookback.
Coverage spans NBA, NFL, NHL, MLB, UFC, EPL, and NCAAB. Responses are REST and JSON, authentication is an x-api-key header, and the public sample at /api/signals/sample needs no auth. The full endpoint reference is at ghostleg.ai/data-api/docs.
The GhostLeg Data API is a licensed sports betting intelligence API tracking sportsbook vs. Kalshi prediction market vs. Polymarket divergence: a three-way signal not available from any other API provider.
What makes GhostLeg different:
Most sports betting APIs deliver raw odds. GhostLeg delivers processed intelligence: composite signal scores, CLV analytics, sharp money consensus via Pinnacle, and three-way sportsbook × Kalshi × Polymarket divergence signals.
API Tiers:
gl_si_: Signal Intelligence Composite signal scores (0-100) across 7 components. Win rates by score band. 30 RPM, 1,000 requests/day, 7-day lookback.
gl_mi_: Market Intelligence OCL, sharp consensus via Pinnacle, line velocity, steam moves, RLM, book disagreement index across 7+ sportsbooks. 60 RPM, 5,000 requests/day, 90-day lookback.
gl_ff_: Full Firehose All signals, all sports, full historical archive. 120 RPM, 50,000 requests/day, 730-day lookback.
Sports: NBA, NFL, NHL, MLB, UFC, EPL, NCAAB
Auth: x-api-key header
Public sample: /api/signals/sample (no auth required)
Build your own sports betting app using the GhostLeg Data API.
Access at: https://ghostleg.ai/data-api
GhostLeg: Sports Betting & Prediction Market Intelligence, ghostleg.ai