McGee started seven of the first nine games but fell out of the rotation about a month into the season and played sparingly the rest of the way.
The Mavericks missed the postseason a year after reaching the Western Conference finals. A midseason trade to pair Kyrie Irving with fellow All-Star Luka Doncic didn't provide a spark, although Dallas re-signed Irving in the offseason.
McGee averaged 4.4 points and 2.5 rebounds in 42 games last season. The 35-year-old has career averages of 7.8 points and 5.2 rebounds.
McGee is a three-time NBA champion, winning twice with the Golden State Warriors as a backup before starting 68 regular-season games for the Los Angeles Lakers in 2019-20. He didn't play in the NBA Finals when L.A. beat the Miami Heat in the playoff bubble.