I also have a 2013 F-150 SCREW short-bed. I have a specifications "sheet" that I found online for 2013 F-150's. It is 15 pages long! There are so many variations of every possible configuration. You really need to look on the labels on your specific truck. The label on the hitch, as has been noted, to tell you the hitch weight capacity, and the label on the driver's side door post for payload capacity. Beyond that you need to know your engine, and whether or not you have 4x4.
Here is your towing specifications guide from Ford.
-Speak