A price on Polymarket belongs to a specific token, which belongs to a market, which belongs to an event. Mixing up the levels is an easy way to compare the wrong numbers with Kalshi. This article summarises how Polymarket's documentation describes these objects. It is not trading advice, and the details can change, so check the current documentation.
Markets
The documentation calls a market the fundamental tradable unit: a resolvable condition with Yes and No outcomes. Every market has a condition ID (a unique identifier for the resolvable condition), a question ID (a hash of the market question used for resolution) and token IDs, ERC1155 token IDs that track positions, one for Yes and one for No. It also notes that a market can only be traded via the order book if enableOrderBook is true.
Events
An event is a container that groups one or more related markets. A single-market event is essentially equivalent to its market. A multi-market event groups related binary questions, and some represent mutually exclusive outcomes, which Polymarket links as a negative-risk group where exactly one market resolves Yes; see negative risk markets.
Which ID for which job
Order book and price data are per token, as the order book response shows a token's asset_id next to the market. The condition ID identifies the market the token belongs to. When you pair a Polymarket outcome with a Kalshi contract, make sure you are holding the token for the same side of the same condition you compared: the Yes token of one market is not the Yes token of the neighbouring market in a multi-market event. The Kalshi series, event and market article covers the other side of the mapping.
A short checklist
- Resolve the pair at the market level, not the event level.
- Take the price from the token of the side you will actually buy.
- Check that the market can be traded through the order book.
- Compare the resolution rules of both markets, not only the titles.
Where Arbitrage Agent fits
Arbitrage Agent matches markets across Kalshi and Polymarket, checks the resolution rules on both sides, and shows the result in a live feed with a step-by-step guide for both legs. You place the orders yourself, and the final check of the details is still yours. See the plans or start with the Starter plan.
Related articles
- Polymarket API Guide
- Polymarket Tick Size and Minimum Order Size
- Polymarket Market WebSocket
- How to Arbitrage Polymarket vs Kalshi
Key terms: Binary Event Market · Resolution Risk