Polymarket Order Book Scraper API - CLOB Bids & Asks

order-book

The full live order book for one market: every bid and ask level with price and size, best bid, best ask, the spread, and the total USD depth standing on each side, plus tick size and minimum order size. Bids and asks are normalised to the same convention on both venues, so a spread is always a real spread. Opt-in with includeOrderBook. Priced above the market row because it is a second live call per market and it is the field traders actually size positions from. Billed once per market per run, and never billed when the book could not be fetched - the market row still arrives, the enrichment simply is not charged.

history

Price history for one market as OHLC candles: open, high, low and close for every period, with volume and open interest per candle, at 1-minute, hourly or daily resolution over a window you choose up to 365 days. Opt-in with includeHistory. This is the depth the incumbent weather-market Actor has an open issue about. Billed once per market per run, never billed when no history could be fetched.

arbitrage

One cross-venue price gap: the same question priced differently on Polymarket and Kalshi, with the cheap side to buy, the dear side to sell, the edge in probability points, the edge as a percentage, the match confidence and the limiting liquidity of the pair. Needs no Kalshi login or password of any kind - the public market data both venues publish is enough - so it cannot break the way credential-based arbitrage Actors do. Pairs are matched conservatively on question wording and refused outright when the numbers in the two questions disagree, because a false pair is worse than a missed one. Billed once per pair per run.

market-check

One market that was actually fetched and compared but billed nothing, because you ran with monitorChangesOnly and its watched fields had not moved since your last run. A tenth of the price of the market row itself - you get the answer, not the data. Charged once per market per run, never on a market that was delivered, and never on a platform call that failed - those stay free and return an error row. This is what keeps an odds watch honest: a quiet tick costs a tenth, and the moment the odds move you are billed for the market exactly as before.