Invoice Validator: VAT Fields, Line-Item Math & EU Compliance Check

{
  "type": "object",
  "required": [
    "vendor_vat",
    "buyer_vat",
    "amounts",
    "line_items"
  ],
  "properties": {
    "amounts": {
      "type": "object",
      "description": "Invoice totals, e.g. { subtotal, tax_amount, total }."
    },
    "currency": {
      "type": "string",
      "description": "Invoice currency code, e.g. \"EUR\". Recommended for full EU compliance validation."
    },
    "due_date": {
      "type": "string",
      "description": "Payment due date (ISO 8601). Recommended for full EU compliance validation."
    },
    "buyer_vat": {
      "type": "string",
      "description": "Buyer's VAT identification number, e.g. \"FR12345678901\"."
    },
    "buyer_name": {
      "type": "string",
      "description": "Buyer's legal name. Recommended for full EU compliance validation."
    },
    "line_items": {
      "type": "array",
      "items": {
        "type": "object"
      },
      "description": "Invoice line items, each with quantity, unit_price, tax_rate, line_total."
    },
    "vendor_vat": {
      "type": "string",
      "description": "Vendor's VAT identification number, e.g. \"DE123456789\"."
    },
    "vendor_name": {
      "type": "string",
      "description": "Vendor's legal name. Required for full EU compliance validation."
    },
    "invoice_date": {
      "type": "string",
      "description": "Invoice issue date (ISO 8601). Required for full EU compliance validation."
    },
    "buyer_address": {
      "type": "string",
      "description": "Buyer's address. Recommended for full EU compliance validation."
    },
    "invoice_number": {
      "type": "string",
      "description": "Invoice number. Required for full EU compliance validation."
    },
    "vendor_address": {
      "type": "string",
      "description": "Vendor's address. Required for full EU compliance validation."
    }
  },
  "additionalProperties": false
}

{
  "type": "object",
  "properties": {
    "valid": {
      "type": "boolean",
      "description": "Overall pass/fail verdict. False if any hard error was found."
    },
    "errors": {
      "type": "array",
      "items": {
        "type": "object",
        "properties": {
          "field": {
            "type": "string",
            "description": "The invoice field the error refers to."
          },
          "issue": {
            "type": "string",
            "description": "Human-readable description of the problem."
          }
        },
        "additionalProperties": true
      },
      "description": "Hard failures (missing required fields, e.g. invoice_number/invoice_date/vendor_name/vendor_address, or failed checks). Empty array, not omitted, when there are none."
    },
    "warnings": {
      "type": "array",
      "items": {
        "type": "object",
        "properties": {
          "field": {
            "type": "string",
            "description": "The invoice field the warning refers to."
          },
          "issue": {
            "type": "string",
            "description": "Human-readable description of the problem."
          }
        },
        "additionalProperties": true
      },
      "description": "Soft issues (missing recommended fields, e.g. buyer_name/buyer_address/due_date/currency) that do not affect `valid` but do affect `eu_compliant`. Empty array, not omitted, when there are none."
    },
    "eu_compliant": {
      "type": "boolean",
      "description": "True only when every recommended field is also present (no warnings) -- observed false on the partial invoice (4 warnings, 4 errors, `valid: false`) and true on the complete one (0 warnings, 0 errors, `valid: true`); both invoices had identical, passing `tax_calculation_check`/`line_items_check` results, so `eu_compliant` here is driven by field completeness, not by the math checks."
    },
    "line_items_check": {
      "type": "object",
      "properties": {
        "failed": {
          "type": "number"
        },
        "passed": {
          "type": "number"
        },
        "total_checked": {
          "type": "number",
          "description": "Number of line items checked."
        }
      },
      "description": "Result of checking each line item's quantity * unit_price = line_total math.",
      "additionalProperties": true
    },
    "tax_calculation_check": {
      "type": "object",
      "properties": {
        "pass": {
          "type": "boolean"
        },
        "actual_tax": {
          "type": "number",
          "description": "The invoice's own reported `amounts.tax_amount`, echoed back."
        },
        "difference": {
          "type": [
            "number",
            "null"
          ],
          "description": "Observed `null` on both real fixtures, tracking `expected_tax`'s null-ness above."
        },
        "expected_tax": {
          "type": [
            "number",
            "null"
          ],
          "description": "Observed `null` on both real fixtures (US/EU sample invoices with a single flat tax_rate line item) -- may only populate when the endpoint can independently recompute an expected tax figure from the line items; unconfirmed when non-null."
        }
      },
      "description": "Result of checking the invoice's reported tax amount.",
      "additionalProperties": true
    }
  },
  "description": "The validation result, as returned at routing.responseResultPath ($.output).",
  "additionalProperties": true
}