The Giants claimed Oaks off waivers from the Royals on Tuesday.
Oaks was designated for assignment by the Royals on Oct. 29 after missing all of 2019 with a hip injury, and he'll now report to San Francisco heading into 2020. The 26-year-old has been effective at Triple-A, recording a 3.23 ERA over 128.1 innings in 2018, but he struggled in his only major-league action, amassing a 7.24 ERA with a 10:6 K:BB in four appearances (two starts).