Henry Schulman of The San Francisco Chronicle reports Uggla's contract is a Triple-A deal with a clause that would allow him to opt out and become a free agent if the Giants don't promote him by August 1.
Uggla was waived last week by the Braves and passed through waivers unclaimed, at which point Atlanta granted him his release.
The three-time All-Star struggled this season with Atlanta. In 48 games he batted .162 with only five extra-base hits.
The Braves signed Uggla to a five-year, $62 million contract in 2011 after he batted .287 with 33 home runs and 105 RBIs in his final season with the Marlins. In four years with Atlanta he never batted better than .233.
- Dan Gartland