Assuming you're talking about a real beading tool, and not the
scraper-with-bead-shaped-cutouts tool...

Beading tools are designed to make beads. You use the edge just like
you'd use the skew's edge, but in theory, the geometry of the beading
tool's shaft helps you roll the bead more easily, if the bead is the
same size as the shaft. I often use my parting tool as a tiny beading
tool this way.

Think of it as a short fat skew that isn't skewed ;-)

The scraper-with-bead-shaped-cutouts tool is for when speed and
consistency are more important than surface quality, or for people who
haven't mastered beads with a skew and would rather do other things,
but need beads anyway.