Create a Custom Field Definition

Create a custom field definition to describe metadata you want to store on shipments or containers.

Request body

Parameter	Required	Description
`entity_type`	Yes	The entity type this field applies to (`Shipment` or `Container`)
`api_slug`	Yes	Unique identifier for the field
`display_name`	Yes	Human-readable name for the field
`data_type`	Yes	Data type for values (for example: `short_text`, `number`, `date`, `reference`)
`description`	No	Optional description of the field’s purpose
`validation`	No	Validation rules (for example: `required`, `pattern`, `max_length`)
`default_format`	No	Default format string for numbers or dates
`default_value`	No	Default value for new custom fields
`reference_type`	No	Required when `data_type` is `reference`