fieldNameStringRequired
The identifier used when reading or writing a value for this extra field.
labelNameStringRequired
The label to display for the extra field.
isRequiredBooleanRequired
Whether a value for this extra field is required.
visibleToEndUserBooleanRequired
Whether the merchant has made this extra field visible to storefront shoppers.
defaultTextStringOptional
The value applied when the shopper supplies none.
rowsIntegerOptional
The number of rows to display for the field, or null if unspecified.