{"demo":true,"source_system":"demo-gateway","meter_device_id":"MTR-DEMO-2048","connection_id":"CONN-DEMO-1002","received_at":"2026-09-19T00:00:00+03:00","reading":{"cumulative_m3":1284.422,"interval_m3":0.083,"flow_m3h":0.19,"quality":"good","actual":true},"status":{"battery_pct":84,"rssi_dbm":-91,"tamper":false,"reverse_flow":false},"adapter":{"name":"demo-open-adapter","version":"1.0.0"},"notice":"Illustrative payload. No live meter is connected."}