Key for Garage works just like Key for Home and Key for Car: An Amazon courier arrives at your home and scans your package, verifying he's at the correct location with the proper order. The garage door opens, the boxes are dropped inside, and the door closes before the delivery person leaves. The customer can monitor the process on the Key app, starting when the package is en-route and following it until the garage shuts. Folks with Cloud Cam can watch it all happen live, too.
You'll need a few things before signing up for Key for Garage. First, it will only work with MyQ-branded Chamberlain or Liftmaster garage door openers, or the MyQ Smart Garage Hub, which adds this connectivity to existing openers. Second, you must live in one of the 37 test cities. Third, you'll need an iota of faith in your fellow man.
But, hey, at least Key for Garage is easier than setting up a city-wide sting operation to catch package thieves, or building a spinning glitter bomb disguised as an Apple Home Pod.