The youngster put pen to paper on a two-year deal on Wearside following the expiration of his contract at Hartlepool United ahead of the 2020-21 season.
Richardson spent part of his younger career in Sunderland's academy before being released.
The right-back made his senior debut back in 2017 with Pools and went on to make 43 appearances, 11 of which were in Sky Bet League Two.