Surface API

The Surface API lets you look up any Kalshi contract ticker or Polymarket contract slug and get the full cross-exchange cluster — every contract in the same group and the relationships between them. Resolution rules are available with include_rules=true. Look up one contract or list a configured scope.

Quickstart

Make your first request in under a minute.

API Reference

Full endpoint reference with interactive playground.

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 one cluster: all contracts in the same cross-exchange group and their links. Contracts are grouped by exchange and ID; links are nested by both exchange and contract ID.

curl https://surfaceapi.com/api/v1/match/KXMLBGAME-26MAR252005NYYSF-SF \
  -H "X-API-Key: YOUR_API_KEY"

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

Overview

Endpoints

Quickstart

API Reference

How it works

Quickstart

API Reference

​How it works

How it works