> ## Documentation Index > Fetch the complete documentation index at: https://docs.surfaceapi.com/llms.txt > Use this file to discover all available pages before exploring further. # Match a contract > Bidirectional cross-exchange contract lookup. Given any contract ID — a Kalshi ticker or a Polymarket contract ID — returns the full cluster: every contract in the same cross-exchange group and the relationships between them. The response is identical regardless of which contract ID in the cluster you query. A match lookup is only counted against your daily quota if it is a **new** cluster — repeated lookups of any ID within the same cluster are always free. Any Kalshi contract ticker or Polymarket contract slug. See [Understanding contract ID](/quickstart#understanding-contract-id) for the difference between tickers and slugs. ## OpenAPI ````yaml GET /match/{contractID} openapi: 3.1.0 info: title: Surface API description: >- Cross-exchange prediction market data. Bidirectional contract matching between Kalshi and Polymarket. version: 1.0.0 servers: - url: https://surfaceapi.com/api/v1 description: Production security: - apiKey: [] paths: /match/{contractID}: get: tags: - Contracts summary: Match a contract description: >- Bidirectional cross-exchange contract lookup. Given any contract ID — a Kalshi ticker or a Polymarket contract ID — returns the full cluster: every contract in the same cross-exchange group and the relationships between them. The response is identical regardless of which contract ID in the cluster you query. A match lookup is only counted against your daily quota if it is a **new** cluster — repeated lookups of any ID within the same cluster are always free. operationId: matchContract parameters: - name: contractID in: path required: true description: Any Kalshi contract ticker or Polymarket contract ID. schema: type: string examples: kalshi: summary: Kalshi ticker value: KXNBAGAME-26MAR07LACMEM-LAC polymarket: summary: Polymarket contract ID value: nba-lac-mem-2026-03-07 responses: '200': description: Cluster found. headers: X-Match-Limit-Remaining: description: Number of new unique cluster lookups remaining today. schema: type: integer X-Match-Limit-Reset: description: RFC3339 UTC timestamp of the next quota reset (midnight UTC). schema: type: string format: date-time content: application/json: schema: $ref: '#/components/schemas/ClusterResponse' example: contracts: - id: KXNBAGAME-26MAR07LACMEM-LAC parent_market_id: KXNBAGAME-26MAR07LACMEM exchange: kalshi question: Los Angeles C at Memphis Winner? yes_name: Los Angeles C no_name: Memphis rules: >- If Los Angeles C wins the game originally scheduled for Mar 7, 2026, this market resolves Yes. - id: KXNBAGAME-26MAR07LACMEM-MEM parent_market_id: KXNBAGAME-26MAR07LACMEM exchange: kalshi question: Los Angeles C at Memphis Winner? yes_name: Memphis no_name: Los Angeles C rules: >- If Memphis wins the game originally scheduled for Mar 7, 2026, this market resolves Yes. - id: nba-lac-mem-2026-03-07 parent_market_id: nba-lac-mem-2026-03-07 exchange: polymarket question: Clippers vs. Grizzlies yes_name: Clippers no_name: Grizzlies rules: >- If the Clippers win, resolves Clippers. If the Grizzlies win, resolves Grizzlies. relationships: - from: KXNBAGAME-26MAR07LACMEM-LAC to: nba-lac-mem-2026-03-07 is_inverse: false - from: KXNBAGAME-26MAR07LACMEM-MEM to: nba-lac-mem-2026-03-07 is_inverse: true '401': description: Missing or invalid API key. content: application/json: schema: $ref: '#/components/schemas/ErrorResponse' examples: missing: summary: No key provided value: error: unauthorized message: Missing API key. Include your key in the X-API-Key header. invalid: summary: Invalid or revoked key value: error: unauthorized message: Invalid or revoked API key. '404': description: >- No cross-exchange match found for this contract. Does not count against your quota. content: application/json: schema: $ref: '#/components/schemas/ErrorResponse' example: error: no_match message: No cross-exchange match found for this contract. '429': description: Daily quota exhausted. headers: X-Match-Limit-Remaining: description: Will be 0. schema: type: integer X-Match-Limit-Reset: description: RFC3339 UTC timestamp of the next quota reset. schema: type: string format: date-time content: application/json: schema: $ref: '#/components/schemas/QuotaErrorResponse' example: error: daily_limit_reached message: >- Free tier limit of 25 new matches per day reached. Resets at midnight UTC. limit: 25 used: 25 resets_at: '2026-03-03T00:00:00Z' '500': description: Internal server error. content: application/json: schema: $ref: '#/components/schemas/ErrorResponse' example: error: internal_error message: An unexpected error occurred. components: schemas: ClusterResponse: type: object required: - contracts - relationships properties: contracts: type: array items: $ref: '#/components/schemas/Contract' description: >- All contracts in this cross-exchange group. Includes all Kalshi contracts and the Polymarket contract they map to. relationships: type: array items: $ref: '#/components/schemas/Relationship' description: >- Directed edges from each Kalshi contract to the Polymarket contract, with inversion flag and confidence. ErrorResponse: type: object required: - error - message properties: error: type: string description: Machine-readable error code. message: type: string description: Human-readable description of the error. QuotaErrorResponse: allOf: - $ref: '#/components/schemas/ErrorResponse' - type: object required: - limit - used - resets_at properties: limit: type: integer description: Your daily quota for new unique cluster lookups. used: type: integer description: Number of new unique clusters accessed today. resets_at: type: string format: date-time description: RFC3339 UTC timestamp of the next quota reset (midnight UTC). Contract: type: object required: - id - exchange - question properties: id: type: string description: The contract identifier on its exchange. parent_market_id: type: string description: >- The parent market or event ID. For Kalshi this is the series+date portion; for Polymarket it is the event slug. exchange: type: string enum: - kalshi - polymarket description: The exchange this contract belongs to. question: type: string description: The market question as displayed on the exchange. yes_name: type: string description: >- Label for the YES outcome (e.g. the team name on a Kalshi moneyline). no_name: type: string description: Label for the NO outcome. rules: type: string description: Resolution rules for the contract. Omitted if not available. Relationship: type: object required: - from - to - is_inverse properties: from: type: string description: Kalshi contract ID. to: type: string description: Polymarket contract ID. is_inverse: type: boolean description: >- When true, YES on the Kalshi contract is equivalent to NO on the Polymarket contract. Invert prices and sides accordingly. securitySchemes: apiKey: type: apiKey in: header name: X-API-Key ````