chest belt
Any belt that is worn on top of clothing or that is part of clothing, that crosses a character's chest. A buckle is required, a strap with no buckle should be tagged as chest strap.
If the belt is part of a chest harness, just use that tag alone, unless there is a separate belt not connected to the chest harness. If the belt crosses the torso diagonally, from above one shoulder to the waist, it is a shoulder belt.
If the belt is directly underneath the breasts/pectorals and touching them, consider adding underbust.If it is not directly under them, use belt instead.