I never bother to define it. Seems a waste of effort IMO.
I title it a corner round tool but define it as a flatmill the same diameter as the little nose of the tool.
Next I program it to do 2.5d profile of the edge to be rounded. Use a cut depth equal to the horizontal runout of the cutter form.
Done deal - simple.
To tweak the blend on the vertical wall use + or - stock in the profile and for the horizontal surface blending go up or down with cut depth.
I use a similar strategy for chamfering - the cutter wants to follow the region to profile without under cutting it so just use negative stock setting to get the cutter to cut the chamfer.
www.integratedmechanical.ca