I am using UPS APIs to figure out ratings and create shipments and now I'd like to track shipments in real time. I know there are a lot of services that provide tracking aggregation for different couriers, including UPS, via webhooks, but I am looking for a "native" UPS API for the real time tracking that would not require me to keep poling for updates.
I went over the UPS API docs and could not find anything. Is there such an API that offers webhook type notifications or something similar in UPS? If not, how do those services like EasyPost, ParcelMonitor, TrackingMore and others can offer such functionality?