Get HIP-4 open interest history

{
  "$schema": "https://json-schema.org/draft/2020-12/schema",
  "title": "getHip4OpenInterest path parameters",
  "type": "object",
  "required": [
    "symbol"
  ],
  "properties": {
    "symbol": {
      "description": "HIP-4 coin id (e.g., `0` for outcome 0 Yes side, `1` for No side). The `#`-prefixed form (`#0`, `#1`) is also accepted.",
      "type": "string",
      "example": "0",
      "x-parameter-location": "path"
    }
  }
}

{
  "$schema": "https://json-schema.org/draft/2020-12/schema",
  "title": "getHip4OpenInterest query parameters",
  "type": "object",
  "properties": {
    "start": {
      "description": "Start timestamp in Unix milliseconds. Defaults to 24h ago.",
      "type": "integer",
      "format": "int64",
      "x-parameter-location": "query"
    },
    "end": {
      "description": "End timestamp in Unix milliseconds. Defaults to now.",
      "type": "integer",
      "format": "int64",
      "x-parameter-location": "query"
    },
    "cursor": {
      "description": "Cursor for pagination",
      "type": "integer",
      "format": "int64",
      "x-parameter-location": "query"
    },
    "limit": {
      "description": "Maximum number of results (default: 100, max: 1000)",
      "type": "integer",
      "default": 100,
      "maximum": 1000,
      "x-parameter-location": "query"
    },
    "interval": {
      "description": "Aggregation interval. When omitted, returns raw ~1 min resolution data.",
      "type": "string",
      "enum": [
        "5m",
        "15m",
        "30m",
        "1h",
        "4h",
        "1d"
      ],
      "x-parameter-location": "query"
    }
  }
}

{
  "$schema": "https://json-schema.org/draft/2020-12/schema",
  "title": "getHip4OpenInterest response 200",
  "description": "API response wrapping an array of HIP-4 per-side open-interest records",
  "type": "object",
  "properties": {
    "data": {
      "type": "array",
      "items": {
        "description": "HIP-4 per-side open-interest record. Mirrors the HIP-3 OI shape and adds `outcome_id` and `side`. `oracle_price` is omitted for HIP-4 (outcomes have no oracle feed). Note: `mark_price` is an implied probability in [0,1], not a USD price; same field name as perps because Hyperliquid upstream uses `markPx` for both.",
        "type": "object",
        "required": [
          "coin",
          "open_interest",
          "outcome_id",
          "side",
          "symbol",
          "timestamp"
        ],
        "properties": {
          "coin": {
            "description": "`#`-prefixed per-side coin identifier",
            "type": "string",
            "example": "#0"
          },
          "mark_price": {
            "description": "Implied probability in [0,1], NOT a USD price. Same field name as perps because Hyperliquid upstream uses `markPx` for both.",
            "type": "string",
            "nullable": true,
            "example": "0.6502"
          },
          "mid_price": {
            "description": "Mid price (probability in [0,1])",
            "type": "string",
            "nullable": true,
            "example": "0.65038"
          },
          "open_interest": {
            "description": "Open interest in contracts (notional currency: USDH)",
            "type": "string",
            "example": "568048"
          },
          "outcome_id": {
            "description": "Numeric outcome identifier",
            "type": "integer",
            "format": "int64",
            "example": 0
          },
          "side": {
            "description": "Side index: 0 = Yes, 1 = No",
            "type": "integer",
            "enum": [
              0,
              1
            ],
            "example": 0
          },
          "symbol": {
            "description": "Same value as `coin`. Provided for consistency with other venues.",
            "type": "string",
            "example": "#0"
          },
          "timestamp": {
            "description": "Snapshot timestamp (UTC)",
            "type": "string",
            "format": "date-time",
            "example": "2026-05-02T20:27:21Z"
          }
        }
      }
    },
    "meta": {
      "description": "Response metadata",
      "type": "object",
      "properties": {
        "count": {
          "description": "Number of records returned",
          "type": "integer"
        },
        "next_cursor": {
          "description": "Cursor for pagination (timestamp). Use this value as the `cursor` parameter to fetch the next page of results.",
          "type": "string",
          "nullable": true
        },
        "request_id": {
          "description": "Unique request ID for support",
          "type": "string",
          "format": "uuid"
        }
      }
    },
    "success": {
      "type": "boolean",
      "example": true
    }
  }
}

{
  "$schema": "https://json-schema.org/draft/2020-12/schema",
  "title": "getHip4OpenInterest response 400",
  "description": "Error response",
  "type": "object",
  "properties": {
    "code": {
      "description": "HTTP status code",
      "type": "integer"
    },
    "error": {
      "description": "Error message",
      "type": "string"
    }
  }
}

{
  "code": 400,
  "error": "Invalid request parameters"
}

{
  "$schema": "https://json-schema.org/draft/2020-12/schema",
  "title": "getHip4OpenInterest response 401",
  "description": "Error response",
  "type": "object",
  "properties": {
    "code": {
      "description": "HTTP status code",
      "type": "integer"
    },
    "error": {
      "description": "Error message",
      "type": "string"
    }
  }
}

{
  "code": 401,
  "error": "Missing or invalid API key. Provide X-API-Key header."
}

{
  "$schema": "https://json-schema.org/draft/2020-12/schema",
  "title": "getHip4OpenInterest response 429",
  "description": "Error response",
  "type": "object",
  "properties": {
    "code": {
      "description": "HTTP status code",
      "type": "integer"
    },
    "error": {
      "description": "Error message",
      "type": "string"
    }
  }
}

{
  "code": 429,
  "error": "Rate limit exceeded"
}