POST requests make sense for packing tracking, you know, because of definition of postal. Okay bad joke but it is true, Google’s package tracking API is now only accepting POST requests. Google updated its documentation to say “Google Package Tracking makes real-time calls (POST requests only) to a RESTful JSON API to retrieve package tracking information.”
Google launched this feature less than a year ago, in December 2019 as a test. It still is an “Early Adopters Program” API but it now only accepts requests via POST.
Google made this change on October 22, 2019, where Google changed the API requirement for package tracking documentation to state that it will only accept POST requests.
So if you are using this feature, make sure you are doing these requests via POST.
Forum discussion at Twitter.