Narwhal API
Economic and commodity odds from both venues in one schema.
Kalshi API and Polymarket API alternatives
Kalshi and Polymarket expose public REST reads without authentication. Each covers one venue, with different formats. Kalshi WebSocket needs signed authentication; Polymarket's market channel is public. A shared schema reduces integration work.
Decision
Choose Narwhal for economic, central bank, metals and energy odds from both venues in one schema. Choose Tatum for another shared interface, PolymarketData for Polymarket history or sports aggregators for sports.
Provider shortlist
Narwhal API is owned and operated by Nusantara Ventures, LLC.
Tatum
Both venues under one key and base URL.
PolymarketData
Historical Polymarket research with order-book snapshots and file exports.
Odds-API.io
Sports prediction odds alongside sportsbook prices.
OddsPapi
Sports fixtures with WebSocket-first bookmaker aggregation.
Oddpool
Existing accounts needing cross-venue analytics and historical order books.
Compare the options
Best fit is not feature parity. Check the evidence and limitation together.
| Provider | Best for | Evidence checked | Important limitation |
|---|---|---|---|
| Narwhal API | Economic and commodity odds from both venues in one schema. | 57 topics through REST and hosted MCP; Basic and Pro add a WebSocket stream. | Free returns the previous day's close for prediction odds; coverage excludes sports, politics and crypto. |
| Tatum | Both venues under one key and base URL. | 24 Polymarket and 14 Kalshi endpoints, with hourly and daily OHLCV candles. | Prediction endpoint pricing and WebSocket support are not published. |
| PolymarketData | Historical Polymarket research with order-book snapshots and file exports. | 1-minute prices, L2 order-book snapshots, a Python SDK and S3 dumps. | Independent Polymarket-only service; no Kalshi coverage. Pricing is not published. |
| Odds-API.io | Sports prediction odds alongside sportsbook prices. | Lists both venues among 415+ bookmakers; paid plans start at $65/month with 5,000 requests an hour. | Prediction coverage is sports only, top of book; new free keys are paused indefinitely. |
| OddsPapi | Sports fixtures with WebSocket-first bookmaker aggregation. | Lists Kalshi and Polymarket among 350+ bookmakers. | Sports fixtures only; free quota is small and paid plans require custom quotes. |
| Oddpool | Existing accounts needing cross-venue analytics and historical order books. | Kalshi and Polymarket analytics include arbitrage, spreads, whale tracking, historical order books and trades, plus WebSocket feeds. | Joined Kalshi in September; new subscriptions are closed. Existing subscriptions and free accounts continue. |
Choose by requirement
Match the market scope
Narwhal covers economic releases, central bank decisions, metals and energy. Odds-API.io and OddsPapi cover sports prediction markets; PolymarketData covers only Polymarket.
Compare history and streaming
Narwhal history supports 1-minute, 5-minute, hourly and daily intervals; Basic and Pro add WebSocket. Tatum lists hourly and daily candles; its WebSocket support is not published.
Allow for venue formats
Kalshi order books return yes and no bids, with string prices. Polymarket Gamma encodes outcome labels, prices and token IDs as JSON strings. Narwhal provides one schema.
Sources and review date
Each detailed provider page lists the first-party documentation used, its evidence boundaries, and its review date.
Reviewed: