{
  "$schema": "https://json-schema.org/draft/2020-12/schema",
  "title": "PurchaseOrderUpdate",
  "type": "object",
  "description": "Request body for updating an existing purchase order. Only provided fields will be modified.",
  "properties": {
    "lineItems": {
      "type": "array",
      "description": "Updated line items"
    },
    "comments": {
      "type": "string",
      "description": "Change request comments"
    }
  }
}