{
  "station": {"id": "OXF", "name": "Oxford"},
  "collected_at": "2026-07-29T09:00:00Z",
  "observations": [
    {"metric": "temperature", "value": 18.2, "unit": "C"},
    {"metric": "humidity",    "value": 71,   "unit": "%"},
    {"metric": "wind",        "value": 12.5, "unit": "km/h"}
  ]
}