{
  "success": true,
  "message": "FRED API proxy: series/observations -> 4 records",
  "data": {
    "realtime_start": "2026-01-01",
    "realtime_end": "2026-03-12",
    "observations": [
      {"date": "2026-03-10", "value": "4.32"},
      {"date": "2026-03-09", "value": "4.28"},
      {"date": "2026-03-06", "value": "4.35"},
      {"date": "2026-03-05", "value": "4.41"}
    ]
  }
}