curl --request GET \
  --url https://api.halal.sh/v1/etfs/{symbol}/purity/history \
  --header 'X-API-Key: <api-key>'

{
  "data": {
    "symbol": "SPY",
    "name": "SPDR S&P 500 ETF Trust",
    "history": [
      {
        "date": "2026-03-01",
        "purity_percentage": 72.5,
        "holdings_total": 503,
        "compliant_count": 289
      }
    ]
  },
  "meta": {
    "request_id": "req_abc123",
    "methodology": "aaoifi-ss21@2024",
    "as_of": "2026-03-08T12:00:00Z",
    "retry_after": 120
  }
}