// MCP tool call — extract_invoice_fields
{
  "jsonrpc": "2.0",
  "method": "tools/call",
  "id": 1,
  "params": {
    "name": "extract_invoice_fields",
    "arguments": {
      "document_id": "doc_a3f9b2c1",
      "fields": [
        "supplier_name",
        "supplier_vat_id",
        "invoice_number",
        "total_amount",
        "vat_amount",
        "issue_date",
        "payment_reference"
      ]
    }
  }
}

// Response
{
  "result": {
    "supplier_name": "Telekom d.d.",
    "supplier_vat_id": "SI12345678",
    "invoice_number": "2024-00847",
    "total_amount": 142.80,
    "vat_amount": 24.80,
    "issue_date": "2024-03-01",
    "payment_reference": "SI00 2024-00847",
    "confidence": 0.97
  }
}