ℹ️ Selecting a Specific Courier
If you have already used our Rates API, you can specify a specific Courier ID to assign a Courier to the Shipment, using the selected_courier_id attribute. If you don’t pass in a Courier ID, we will return a list of all possible Rates to your new Shipment and assign the best value for money Courier to your Shipment.

ℹ️ Calculating Dimensions and Total Weight
If a parcel's total_actual_weight is provided, it will prevail over the sum of the items' weights. If not provided, the items' weights are mandatory and will be used to calculate the total package dimensions.

Likewise, if the box object is provided, its dimensions will prevail over all individual items' dimensions. If a box isn't specified, item dimensions are mandatory and we will used to determine the best box for the parcel.

Note: If the shipment contains an item with batteries, item.actual_weight is mandatory regardless of whether total_actual_weight is provided. This is because couriers require more accurate information on an item-level when shipping dangerous goods.
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