{
 "model_version": "2026-10-23 (monthly PVGIS profile, optional grid-charging power limit, optional load shifting without a battery)",
 "protocol_version": "2025-06-18",
 "note": "Synthetic regression example, not a current tariff offer. Initialise the MCP session before tools/call.",
 "request": {
  "jsonrpc": "2.0",
  "id": 2,
  "method": "tools/call",
  "params": {
   "name": "calculate_payback",
   "arguments": {
    "annual_use_kwh": 3650,
    "daytime_share": 0.4,
    "cheap_hours_share": 0,
    "solar_kwh_per_year": 0,
    "battery_usable_kwh": 13.5,
    "round_trip_efficiency": 0.9,
    "peak_rate_p": 26.32,
    "cheap_rate_p": 8,
    "export_rate_p": 0,
    "battery_price_gbp": 6500
   }
  }
 },
 "expected": {
  "yearly_saving_gbp": 381.74,
  "payback_years": 17.0
 },
 "verification": "/api/v1/test-cases.json"
}