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The Surface API lets you look up any Kalshi contract ticker or Polymarket contract ID and get the full cross-exchange cluster — every contract in the same group, their resolution rules, and the relationships between them. One endpoint. Works in any direction.

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API Reference

Full endpoint reference with interactive playground.

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How it works

Surface maintains a continuously updated dataset of matched contracts across Kalshi and Polymarket. Every match passes through a multi-stage pipeline that checks team, date, line, and side alignment — mismatches are blocked, not returned. When you call /match/{contractID}, Surface resolves the input and returns the full cluster: all contracts in the same cross-exchange group and the relationships between them. The response is identical regardless of which contract ID you query. 
curl https://surface.surf/api/v1/match/KXMLBGAME-26MAR252005NYYSF-SF \
  -H "X-API-Key: YOUR_API_KEY"

{
  "contracts": [
    {
      "id": "KXMLBGAME-26MAR252005NYYSF-SF",
      "parent_market_id": "KXMLBGAME-26MAR252005NYYSF",
      "exchange": "kalshi",
      "question": "New York Y vs San Francisco Winner?",
      "yes_name": "San Francisco",
      "no_name": "NO: San Francisco"
    },
    {
      "id": "mlb-nyy-sf-2026-03-25",
      "parent_market_id": "mlb-nyy-sf-2026-03-25",
      "exchange": "polymarket",
      "question": "New York Yankees vs. San Francisco Giants",
      "yes_name": "New York Yankees",
      "no_name": "San Francisco Giants"
    },
    {
      "id": "KXMLBGAME-26MAR252005NYYSF-NYY",
      "parent_market_id": "KXMLBGAME-26MAR252005NYYSF",
      "exchange": "kalshi",
      "question": "New York Y vs San Francisco Winner?",
      "yes_name": "New York Y",
      "no_name": "NO: New York Y"
    }
  ],
  "relationships": [
    { "from": "KXMLBGAME-26MAR252005NYYSF-SF", "to": "mlb-nyy-sf-2026-03-25", "is_inverse": false },
    { "from": "KXMLBGAME-26MAR252005NYYSF-NYY", "to": "mlb-nyy-sf-2026-03-25", "is_inverse": true }
  ]
}

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Coverage

CategoryMarkets
SportsMLB, NBA, NHL, UFC, PGA Tour, NCAAB