Prediction market arbitrage bot: free API + MCP
Skip the scraping. Poll live Polymarket, Kalshi and PredictIt arbitrage from one free JSON endpoint or an MCP tool, and point your bot straight at the matched pairs.
Most arbitrage bots spend their first week just collecting data: scraping each venue's order book, normalizing outcomes, and fuzzy-matching the same real-world event across Polymarket, Kalshi and PredictIt. This board already does all of that and exposes the result as a free JSON API and an MCP tool, so your bot starts at the interesting part: deciding which spreads to take.
Hit /api/v1/arbitrage and you get every matched pair with each leg's venue, live Yes/No price, the combined cost, and whether it is a live arbitrage (combined cost under $1). Poll it on your own cadence, filter by ROI or minimum volume, and route the two legs to your execution layer. The same data is an MCP tool (get_arbitrage), so an AI agent can call it directly inside a reasoning loop and act without any glue code.
It is a scanner and a data feed, not an execution engine: we surface verified, resolution-matched opportunities and leave the trading to you. Mind the real-world frictions a good bot models: fees, gas on Polygon, thin order-book depth at the mispriced level, and slight differences in how each venue resolves an event, any of which can turn a paper edge into a loss.
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Free arbitrage API and MCP tool for bots
Every match on this page is also a free JSON endpoint and an MCP tool, so a trading bot or AI agent can poll live opportunities and act on them without scraping each venue.
Questions
- How do I build a Polymarket arbitrage bot with this?
- Poll
/api/v1/arbitrage(or call theget_arbitrageMCP tool), filter the response foris_arbitrage: trueand your minimum ROI, then send each leg'surlor market id to your own execution/wallet layer. The feed handles discovery and matching; you handle the trade. - Is the arbitrage API free?
- The discovery feed (matched pairs, prices, links, ROI) is free with no signup and CDN-cached for fast polling. Native venue market ids for programmatic execution are a paid add-on.
- Which venues does the bot API cover?
- Polymarket, Kalshi (and Robinhood, which trades on Kalshi’s exchange), and PredictIt, every market normalized to a single Yes/No price and matched to the same real-world event.
- Can an AI agent use it directly?
- Yes.
get_arbitrageis an MCP tool, so an agent can call it in-loop, read the live spreads, and decide, no scraping or custom integration required. - Do arbitrage bots actually make money on prediction markets?
- Fast bots do capture real spreads, but the edges are small and short-lived and frictions (fees, gas, thin liquidity, resolution differences) erase sloppy ones. The advantage here is starting from verified, resolution-matched pairs instead of raw noise.