{
  "name": "WGL Holdings Customer Account",
  "description": "Structure of a WGL Holdings customer account for natural gas or electricity service.",
  "fields": [
    { "name": "accountNumber", "type": "string", "required": true, "description": "Unique customer account identifier." },
    { "name": "serviceType", "type": "string", "enum": ["NaturalGas", "Electricity", "DualFuel"], "required": true },
    {
      "name": "serviceAddress",
      "type": "object",
      "required": true,
      "fields": [
        { "name": "street", "type": "string", "required": true },
        { "name": "city", "type": "string", "required": true },
        { "name": "state", "type": "string", "required": true },
        { "name": "zip", "type": "string", "required": true }
      ]
    },
    { "name": "customerType", "type": "string", "enum": ["Residential", "Commercial", "Industrial"], "required": true },
    { "name": "utilityProvider", "type": "string", "enum": ["WashingtonGas", "WGLEnergyServices"], "required": true },
    { "name": "rateSchedule", "type": "string", "required": false },
    { "name": "meterNumber", "type": "string", "required": false },
    {
      "name": "usageHistory",
      "type": "array",
      "required": false,
      "items": {
        "type": "object",
        "fields": [
          { "name": "billingPeriodStart", "type": "string", "format": "date", "required": true },
          { "name": "billingPeriodEnd", "type": "string", "format": "date", "required": true },
          { "name": "usage", "type": "number", "required": true },
          { "name": "unit", "type": "string", "enum": ["Therms", "CCF", "KWh"], "required": true },
          { "name": "billedAmount", "type": "number", "required": false }
        ]
      }
    },
    {
      "name": "contractDetails",
      "type": "object",
      "required": false,
      "fields": [
        { "name": "contractType", "type": "string", "enum": ["Fixed", "Variable", "Indexed"], "required": false },
        { "name": "startDate", "type": "string", "format": "date", "required": false },
        { "name": "endDate", "type": "string", "format": "date", "required": false },
        { "name": "pricePerUnit", "type": "number", "required": false },
        { "name": "unit", "type": "string", "required": false },
        { "name": "renewablePercentage", "type": "number", "required": false },
        { "name": "carbonNeutral", "type": "boolean", "required": false }
      ]
    },
    {
      "name": "contact",
      "type": "object",
      "required": false,
      "fields": [
        { "name": "name", "type": "string", "required": false },
        { "name": "email", "type": "string", "format": "email", "required": false },
        { "name": "phone", "type": "string", "required": false }
      ]
    }
  ]
}