I've shot many foxes using a .22lr. The main ammo I currently use is CCI Minimag hollowpoints & you wont have any problems dropping foxes to 75 yards. I also have a .17hmr & this increases the range to 150 yards for foxes. My 22-250 will kill foxes as far away as I can hit them.
Foxes will sometimes come to a call. I have a couple of cheap tin fox whistles that I usually keep in a pocket or pack. These whistles will sometimes even momentarily stop a fleeing fox giving just enough time for a shot.
I'd say if you bought a cheap fox whistle & had any .22lr high velocity hollowpoints that shoot accurately through your gun, then you are good to go fox hunting.