Oddpool

What it is

A cross-venue data layer over Kalshi and Polymarket, sold two ways that are now far apart. The public half is a website of free dashboards that price the same event on both venues side by side, plus a metered REST and WebSocket API. The half the home page now leads with is institutional: a tick-level order-book archive and a reference-data registry that gives the same outcome on Kalshi, Polymarket and Polymarket US one canonical id, delivered by REST, WebSocket or daily Parquet files to your own bucket, priced on a call.

The API is conventional for this category. Search runs across both venues by text or by series id (KXBTC15M on Kalshi, btc-up-or-down-15m on Polymarket); historical endpoints return full order-book snapshots, a top-of-book time series and the trade tape per venue; OHLCV bars come in 6-hour, daily, weekly and monthly intervals for up to 50 markets a call. The WebSocket is the more interesting design: channels are addressed by event rather than by venue ticker — dist:fomc-2026-04-29 rather than a Kalshi ticker and a Polymarket token — and both venues arrive on the same channel tagged by a venue field. Two feeds are documented, a macro feed (FOMC, CPI, payrolls, GDP, unemployment) and a crypto feed that attaches a Binance spot and futures reference price to every BTC and ETH message.

On the website there are dashboards for over 750 events, an arbitrage scanner and a price-spread view across Kalshi, Polymarket and Opinion, a whale-trade tracker, paper trading with 10,000 virtual dollars against live prices, and Oddbot, a chat assistant launched on 6 May 2026 that answers from the same data.

The publisher is Oddpool, Inc., which its privacy policy names and whose terms are governed by Delaware law. The home page carries a Y Combinator logo under "Backed by".

Availability

An account and an API key, with no identity check and no geographic restriction in the Terms of Service or the privacy policy we read on 30 September 2026. Nothing here is a venue, so there is nothing to deposit and no jurisdiction question about the data itself — only about whether you may trade on what you read, which is the venue's question and sits on the Kalshi and Polymarket cards.

The API is live and gated: an unauthenticated request to api.oddpool.com/search/events answered 401 with "Authentication required (API key or signature)" on 30 September 2026.

New paid subscriptions are closed. On the same day the pricing page said "Oddpool is no longer accepting new subscriptions. Existing subscriptions and free accounts continue as normal", and both Pro and Premium were marked not available. The notice is absent from a Wayback capture of 10 June 2026 and present in one of 31 August 2026, so it went up somewhere in that window. A new reader today can have the free tier or an enterprise conversation, and nothing between.

Pricing

Four published tiers, two of them closed to new subscribers.

• Free — $0. The dashboards, search, historical data, paper trading and about 30 Oddbot chats a month. 1 request a second and 1,000 API requests a month as a hard cap, one key, one WebSocket connection limited to the dist channel for two events at a time.
• Pro — $30 a month, closed. 10 requests a second, 1 million a month, three connections on all channels for ten events, and the arbitrage, spread, volume and whale dashboards plus the whale API.
• Premium — $100 a month, closed. 25 requests a second, 5 million a month, ten connections and unlimited events, and the arbitrage and price-spread APIs.
• Enterprise — priced on a call. 500 requests a second, unlimited quota, tick-level microstructure data, S3 dumps, custom delivery and SLAs.

1,000 requests a month is roughly one request every 45 minutes. It is enough to evaluate the schema and pull a handful of books, and not enough to poll anything; with the paid tiers shut, the next step up from the free tier is a sales call.

Oddpool charges no trading fee because it executes nothing. Every fill is the venue's.

Markets & resolution

Whatever Kalshi and Polymarket list — elections, sports, macro releases, crypto price windows and awards. The home page claims search over more than 700,000 markets. Oddpool resolves and settles nothing, so resolution_source is null, and settlement lists both types because the two venues do not share one: Kalshi pays in dollars, Polymarket in pUSD on-chain.

The most useful sentence on the vendor's site is about exactly that. On a sample of 250 matched events, the institutional page says only about a third were settlement-fungible across both venues; the rest differed in the settlement window (a different deadline) or the settlement universe (different bucket boundaries or candidate set). A price gap between two such listings is a difference in contract terms before it is anything else, and the free dashboards and the arbitrage scanner present them side by side. The reference-data product records that classification per pair; it is enterprise-only, and every call to it without an institutional key returns 403.

History starts late. The documented API holds Kalshi from 19 March 2026 and Polymarket from 20 March 2026, published about an hour after the fact, and the vendor states that neither venue offers a backfill — the archive exists only from the day Oddpool started recording.

Integrations

REST at api.oddpool.com with the key in an X-API-Key header, a WebSocket at feeds.oddpool.com/ws authenticated by a message after connecting, and cursor pagination on the historical endpoints. dist, book and trade channels are change-driven, so a quiet channel is silent, and a snapshot channel delivers full state every 60 seconds — on paid tiers only. The enterprise tier adds daily Hive-partitioned Parquet for DuckDB, Polars, Spark or a Snowflake share.

No SDK in any language and no data MCP server. The documentation publishes an llms.txt index for coding agents instead; the MCP entry on the docs site is the documentation host's own search integration, not access to the data.

There is no alert channel either. The arbitrage landing page promises "instant alerts" and a notification, but on 1 October 2026 no row of the pricing table, no changelog entry and no documentation page described an email, push or Telegram notification, and the pricing FAQ presents a Telegram alert as something you build yourself on Premium. The alerts flag is off for that reason.

Limitations

The terms and the documentation disagree about what you may build. The Terms of Service, last updated 11 March 2026, say you may not use the Service for trading automation, and license all data — arbitrage opportunities, spreads, whale trades, historical snapshots — for personal, internal use only, with no redistribution or incorporation into another product. The documentation pitches arbitrage bots that "execute automatically", copy trading off the whale feed and alert bots, and the pricing page's own FAQ describes Premium as "built for automated strategies". Until the vendor reconciles the two, the contract is the terms.

The arbitrage endpoint is a trade instruction, not a measurement. It returns "buy YES here, buy NO there" with a per-contract net after fees, and its documentation describes the result as profit locked in. What it models is the top 25 ask levels and each venue's fee schedule; what it does not model, by its own note, is latency, partial fills or order minimums — and, from the paragraph above, whether the two listings settle on the same terms at all. Resolution risk on the two legs is the risk that remains.

The retail product has stopped taking money. The changelog's last entry is Oddbot on 6 May 2026 and the research page's last article is dated 28 May 2026; paid plans closed between June and August. A free tier on a vendor that has turned toward institutional sales is a tier with no stated commitment behind it.

Oddbot is marketed as a research tool with an opinion. The launch note says it will "pressure-test a trade thesis" and "point at the cleanest market to express it". This card carries ai_features: research because what it is documented to do is look up prices, history, whale flow and spreads and cite them; the market-choosing line is the part to read with care. We have not used it.

Two venues. Anyone who wants Limitless, Myriad or Manifold in the same schema is at the wrong card, and Opinion appears only in the arbitrage scanner.

Alternatives

FinFeedAPI normalizes nine venues rather than two and sells requests with no closed tiers, but has no WebSocket on this product. Adjacent covers the same two venues with indices and reference rates, and publishes a free delayed tier and paid plans you can still buy. Predexon sells tick-level book history as Parquet by the gigabyte across more venues, with an archive starting at almost the same point in March 2026. PMXT is open source and can be run on your own machine against the venues directly. The venues' own feeds — the Kalshi API and the Polymarket Gamma API — are free and deeper, at the cost of doing the cross-venue matching yourself, which is the one thing Oddpool is actually selling.