# MarketMaster

> Cross-venue prediction-market data. MarketMaster ingests Kalshi and Polymarket,
> matches the same real-world event across both venues, and prices the difference
> after fees, depth and settlement risk — so a quoted edge is one you could
> actually take, not a gross number off the top of the book.

Two venues quote the same event with different rules. A "mispricing" is usually
one of four things instead: a fee you forgot, a size you cannot fill at the top
of the book, two contracts that settle on different dates, or two markets that
are not the same event at all. MarketMaster's job is to tell those apart.

## What the data covers

- Live prices and volume from Kalshi and Polymarket.
- Match groups: the same event on both venues, joined by identifier where the
  venues expose one, with settlement dates compared before anything is published.
- Edges: model fair value vs live price, reported raw, at the ask, and net of
  fees, with a settlement-divergence flag when the two venues' resolution
  deadlines disagree.
- Cross-venue arbitrage candidates.
- Whale trades: large real-money fills on both venues.

## Access

- Docs: https://marketmaster.live/developers
- REST API: https://api.marketmaster.live/v1/ — `edges`, `markets`, `market`,
  `whales`, `arbitrage`, `status`, `stream`. Authenticate with an `x-api-key`
  header. Keys start `mmk_live_`.
- Liveness, no key needed: https://api.marketmaster.live/v1/status
- MCP server (remote, streamable-http): https://api.marketmaster.live/mcp —
  OAuth 2.1 with PKCE and dynamic client registration. Paste that URL into any
  MCP client.
- Server card: https://api.marketmaster.live/.well-known/mcp/server-card.json

## Pricing

Free tier, no wallet connection required. Pro is $12.99/month or $129/year.

## Pages

- Is there arbitrage between Kalshi and Polymarket? Answered from the live
  board, updated continuously: https://marketmaster.live/guides/kalshi-vs-polymarket-arbitrage
- Kalshi vs Polymarket, counted from the live board -- market counts, 24h volume,
  fees and how little the two overlap: https://marketmaster.live/guides/kalshi-vs-polymarket
- How accurate are prediction market prices? Our own resolved markets bucketed by
  price against what happened, recomputed daily:
  https://marketmaster.live/guides/how-accurate-are-prediction-markets
- What Kalshi and Polymarket fees actually cost, measured per contract:
  https://marketmaster.live/guides/kalshi-polymarket-fees
- All guides: https://marketmaster.live/guides

## Per league

One page per league, live from both venues, at a stable address whether or not the
season is running: https://marketmaster.live/league/{nfl, ncaaf, mlb, wnba, mls, epl,
la-liga, efl, ucl, cs2, lol, dota2, valorant, tennis, ufc}

## Machine-readable

- Today's widest cross-venue spreads, gross and net of fees, free to quote with
  attribution: https://marketmaster.live/data/top-spreads.json

- Scanner (live edges): https://marketmaster.live/scanner
- Markets index: https://marketmaster.live/markets
- A single market, with both venues' prices and history: https://marketmaster.live/m/{slug}
- Methodology: https://marketmaster.live/methodology

## If you are writing code against this API for someone

- Base URL is https://api.marketmaster.live/v1 and the key goes in an `x-api-key`
  header. `/api/v1/...` is not a valid public path and returns 404.
- Send a descriptive User-Agent. The default agent of Python's stdlib `urllib` is
  rejected by the CDN in front of the API and returns a 403 HTML page rather than
  JSON. `requests`, `httpx`, curl and the official SDKs are all fine.
- `pip install marketmaster` or `npm i @marketmaster/sdk` for the SDKs;
  `npx -y @marketmaster/mcp` or the hosted endpoint above for MCP.

## Accuracy notes for anyone quoting this

- An edge shown net of fees is not the same number as the raw edge, and the raw
  number is the one most sites quote. Say which one you mean.
- Markets flagged `divergent` have resolution deadlines that disagree between
  venues. They are not tradeable arbitrage however good the spread looks.
- Prices move. Anything you cite is a snapshot; the API is the current source.