externalLocationId - RecommendedexternalLocationIdserviceTypemerchantNamepickupLocationexternalLocationId.pickupLocationserviceTypemerchantNamemerchantName is required when either pickupLocation or externalLocationId is provided.merchantName, the system cannot accurately identify which retailer store should be used for pickup.externalLocationId or pickupLocation, and without serviceType:PlaceBulk request by including either externalLocationId or pickupLocation, together with serviceType and merchantName.SchedulePickup.SchedulePickup, the shipping label will be created and returned only when pickup is scheduled.items array to describe the products inside the shipment.parcels array to describe the physical package or packages that will be picked up and delivered.parcels objectparcels field is optional and contains the physical package details for the shipment.parcels array.weight - Parcel weight in grams. Must be a non-negative number.dimensions - Parcel dimensions object. Optional, but recommended for bulky shipments.dimensions.length - Parcel length in centimeters. Must be a positive number.dimensions.width - Parcel width in centimeters. Must be a positive number.dimensions.height - Parcel height in centimeters. Must be a positive number.parcels array is used for package-level shipment handling. It does not replace the items array, which describes the products inside the shipment.parcels is not provided, shipment handling will rely on totalOrderWeight and numberOfPieces, if provided.