The Giants selected Cox's contract from Double-A Richmond on Sunday.
The 24-year-old outfielder will skip over Triple-A and head to the majors after producing a monstrous .400/.453/.644 with six home runs and 27 stolen bases across 183 plate appearances in the Eastern League, though Cox's production comes with the caveat that he was older than most of his peers at Double-A. The right-handed hitter isn't in the lineup Sunday while the Giants face off against Colorado righty Tanner Gordon, so Cox could be in line for a short-side platoon role to begin his MLB career.