{
  "$schema": "https://json-schema.org/draft/2020-12/schema",
  "type": "object",
  "properties": {
    "request_id": { "type": "string" },
    "quantity": { "type": "number" },
    "delivery_date": { "type": ["string", "null"] }
  },
  "required": ["request_id", "quantity", "delivery_date"]
}