Mules are slightly smaller than their horse parent, and when they grow they share traits of both a donkey (the long ears), and the horse (color, tail, etc.). A Mule in the grass.
For example, a 2014 Ford F-150 is considered a half ton truck but most variants can carry a lot more than 1,000 pounds in the bed. Since these terms are probably not going away any time soon, it's best just to think of them as smaller, mediumest, and more than medium.. (Pause for laughter).
Modern half-ton trucks are pretty much the GVWR Class 2 list; Ford F-150, Chevrolet Silverado 1500, GMC Sierra 1500, Ram 1500, Toyota Tundra, and Nissan Titan. Today these trucks tend to have a curb weight (weight empty but ready-to-drive) around 5,000+ pounds and payload capacities between 1,000 and 3,000 pounds. Manufacturers tend to claim they can tow between 5,000 and 10,000+ pounds.