{
  "symbol": "US30",
  "display": "US30",
  "asset_class": "indices",
  "timeframe": "M30",
  "rows": 82684,
  "start": "2019.07.16 07:30:00",
  "end": "2026.10.09 20:30:00",
  "score": 90.2,
  "grade": "A",
  "critical_count": 0,
  "warning_count": 3,
  "checks": {
    "duplicates": 0,
    "out_of_order": 0,
    "ohlc_violations": 0,
    "nonpositive_prices": 0,
    "flat_bars": 7,
    "flat_bars_pct": 0.008,
    "zero_volume": 0,
    "zero_volume_pct": 0.0,
    "zero_spread": 2,
    "zero_spread_pct": 0.002,
    "negative_spread": 0,
    "extreme_returns": 0,
    "gaps": 1495,
    "largest_gap_seconds": 55800,
    "largest_gap_start": "2020.03.15 22:00:00",
    "weekend_bars": 1016
  },
  "issues": [
    {
      "severity": "warning",
      "check": "gaps",
      "count": 1495,
      "message": "Gap greater than 2x timeframe and under 24h"
    },
    {
      "severity": "warning",
      "check": "zero_spread",
      "count": 2,
      "message": "Zero or missing spread"
    },
    {
      "severity": "info",
      "check": "flat_bars",
      "count": 7,
      "message": "Open=High=Low=Close"
    },
    {
      "severity": "warning",
      "check": "weekend_bars",
      "count": 1016,
      "message": "Invalid weekend bars for this asset class"
    }
  ],
  "generated_at": "2026-11-01",
  "report_url": "/historical-data/data-quality/detail.php?symbol=US30&tf=M30"
}