Offer time-definite last-mile delivery windows to consumers at checkout using a carrier delivery appointment API

Steps

1. At checkout, call the UPS My Choice for Business delivery preferences API or the UPS Access Point locator API to determine available delivery window options for the consignee's address
2. Present the consumer with available delivery window slots (e.g., morning, afternoon, evening) or UPS Access Point pickup locations as checkout options
3. Record the consumer's chosen delivery preference and pass it as the delivery instructions or service options field in the UPS Shipping API label creation request
4. After label purchase, register the shipment with UPS My Choice if the consignee is enrolled so they can manage their own delivery window preference
5. Listen for UPS Track Alert webhook events to detect when a delivery appointment is confirmed or changed by the carrier, and surface updates to the consumer
6. Handle fallback gracefully: if the delivery window service is unavailable for a given service type or ZIP code, fall back to standard delivery without exposing the API error to the consumer