{
  "type": "object",
  "title": "PurchaseOrderSchema",
  "description": "Structured-extraction schema for purchase orders.",
  "properties": {
    "document_number": { "type": ["string", "null"] },
    "date": { "type": ["string", "null"] },
    "delivery_due_date": { "type": ["string", "null"] },
    "payment_due_date": { "type": ["string", "null"] },
    "supplier": {
      "type": ["object", "null"],
      "properties": {
        "name": { "type": ["string", "null"] },
        "tax_id": { "type": ["string", "null"] },
        "address": { "type": ["string", "null"] }
      }
    },
    "customer": {
      "type": ["object", "null"],
      "properties": {
        "name": { "type": ["string", "null"] },
        "tax_id": { "type": ["string", "null"] },
        "address": { "type": ["string", "null"] }
      }
    },
    "line_items": {
      "type": "array",
      "items": {
        "type": "object",
        "properties": {
          "item_code": { "type": ["string", "null"] },
          "description": { "type": ["string", "null"] },
          "quantity": { "type": ["number", "null"] },
          "unit": { "type": ["string", "null"] },
          "unit_price_net": { "type": ["number", "null"] },
          "total_net": { "type": ["number", "null"] }
        }
      }
    },
    "total_net": { "type": ["number", "null"] },
    "total_vat": { "type": ["number", "null"] },
    "total_gross": { "type": ["number", "null"] },
    "_quotes": { "type": "array", "items": { "type": "string" } },
    "_confidence": { "type": "object" },
    "_source": {
      "type": "object",
      "properties": {
        "file_name": { "type": "string" },
        "page_number": { "type": ["integer", "null"] }
      }
    }
  },
  "required": ["_quotes", "_confidence"]
}