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The Reference Data API is an enterprise product for institutional customers. It is separate from the retail Oddpool API and is not available on consumer plans. Access requires an institutional agreement and a reference-data-enabled API key. Contact avi@oddpool.com for access.
Kalshi, Polymarket, and other venues each give the same event a different ticker, ID, and question text. The Reference Data API matches them and gives you:
  • one ID per event: the same game, election, or Fed decision across every venue that lists it
  • one ID per outcome: each named answer on that event
  • one ID per entity: the team, person, or party an outcome refers to, with a Wikidata Q-ID
  • the venue tickers you need to subscribe to live prices on each side
For each matched event, it also tells you where the two venues agree and where they settle differently, so you can size a cross-venue position knowing exactly how fungible the two sides are. That classification is documented on List matched events and returned on every event.

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Base URL and auth

Every request needs your API key in the X-API-Key header and returns JSON:
A 401 means the key is missing or unknown; a 403 means the key is valid but doesn’t include reference-data access (or its trial has expired).

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Quickstart

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Endpoints

Get Oddpool ID by ticker

Turn a Kalshi, Polymarket, or Polymarket US id into the matched event, with every outcome and venue side.

List matched events

Page live or historical events, filtered by venue pair and fungibility.

Look up an entity

Look up a team, person, or party by Wikidata Q-ID, Oddpool ID, or name.

Search entities

Find entities by substring and kind.

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How a response is shaped

Every event response nests four layers, each with its own Oddpool ID:
  • Event (OPI): one real-world resolution, like a game, election, or Fed decision
    • Outcome (OPO): one named answer on the event, like a team, “Yes”, or a price bucket
      • Venue listing (OPL): one venue’s tradeable side of that outcome, the ticker you trade
      • Entity (OPE): the team, person, or party the outcome refers to

Supported venues

The venue tags you can pass to venue and venue_pair, and how they combine.

Oddpool IDs

What OPI, OPO, OPL, and OPE identify, how they nest, and why they’re safe to cache.

Response fields

Definitions for every field in the event and entity responses, including basis_class, outcome kinds, and divergence.