Exchange prices belong in your model.
No other odds API ships them.

Five exchanges, two market structures

We normalize prediction-market contracts (Kalshi, Polymarket) and back/lay or P2P exchanges (Smarkets, Matchbook, Novig) into the same bookmakers[].markets[].outcomes[] shape the rest of the API uses. No special-casing on your side.

Exchanges quote game lines, not player props — props live with the sportsbooks in the same response. We tell you the real shape rather than overpromising prop coverage exchanges don't have.

Sample — exchanges next to the books

Same response shape the-odds-api uses, so migrating is a base-URL swap. Filter to exchanges only with &bookmakers=kalshi,polymarket,smarkets,matchbook, or keep them alongside Pinnacle and the soft books for a full sharp-vs-soft-vs-exchange screen.

# Exchanges + sportsbooks, one call, same schema
GET https://api.prop-line.com/v1/sports/baseball_mlb/odds
  ?markets=h2h,totals
  &apiKey=YOUR_KEY

→ bookmakers: [
    { "key": "kalshi",     "title": "Kalshi",     "markets": [ /* event-contract */ ] },
    { "key": "polymarket", "title": "Polymarket", "markets": [ /* on-chain      */ ] },
    { "key": "smarkets",   "title": "Smarkets",   "markets": [ /* back price    */ ] },
    { "key": "matchbook",  "title": "Matchbook",  "markets": [ /* back price    */ ] },
    { "key": "novig",      "title": "Novig",      "markets": [ /* P2P exchange  */ ] },
    { "key": "pinnacle",   "title": "Pinnacle",   "markets": [ /* sharp book    */ ] },
    { "key": "draftkings", "title": "DraftKings", "markets": [ /* soft book     */ ] }
  ]

pip install propline

from propline import Client
c = Client(api_key="...")
odds = c.get_odds(
  sport="baseball_mlb",
  markets="h2h,totals",
  bookmakers="kalshi,polymarket",
)

npm install propline

import { Client } from "propline";
const c = new Client({ apiKey: "..." });
const odds = await c.getOdds({
  sport: "baseball_mlb",
  markets: "h2h,totals",
  bookmakers: "kalshi,polymarket",
});