Generate a shipping label with a tracking number for a specific carrier and service. This is the core endpoint for creating shipments — it returns a printable label and registers the shipment with the carrier.

When to use: Call this endpoint after you have selected a rate from the /ship/rate/ response and are ready to create an actual shipment.

Prerequisites:

• Valid JWT authentication token (Bearer)
• A selected carrier and service (typically from a prior rate quote)
• Complete origin and destination addresses
• Package dimensions and weight
• For international shipments: customs items information and content description

Key behaviors:

• Returns a label URL (PDF), tracking number, and shipment metadata
• Once generated, the label is registered with the carrier and may incur charges
• Cancel unused labels via /ship/cancel/ to request a refund
• Supports additional services (insurance, signature, etc.) through the settings object
• For international DDP shipments, include duty/tax payment details in the request