Overloaded - I am not sure what you are saying. Are you saying that you are wanting to put a radius on the end of a bar i.e. a 1 inch bar with a rounded end at 1/2 inch radius.
I do not see how you can achieve this with a sharp pointed tool which I take is a straight V shape. You need, for the picture you are showing, a tool that is cranked left, and I would suggest, a smooth radius tip of at least 90 degrees. Unles your toolholder moves as it describes an arc, then a different part of the tool must come in touch with the workpiece as it moves around.
I generally cut mine the other way, from the centre, outwards, and the tool first makes contact on its left hand side, and then as it works round, the point of contact gradualy moves to the top of the tool, to the right of centre.
Unfortunately, without some very sophisticated (sorry Art if you have done this) calculation, the result will not be a perfect circle, because you start at the true radius (the side of the tool touching the end of the work at X0 Z0), then as you come round to the side of the work the width of the tool tip comes into play and the radius is short and the tool cuts into the bar.
The answer is (I think) say with a tip of 0.125 radius is to start round from X0 Z0 - with the side of the tool touching the work, but add on the tool tip width when writing the code - I.E. CALL THE START POINT X0 Z0.125. The code would then be, from that start point G2 Z-0.5 X0.625 R0.625. The radius of the arc the tool describes is always the radius you want, plus the tool tip radius. I have used a large radius tool tip here to better illustrate the point.
As long as you use a cranked tool, the offset radius is always equal on both axis, so you could, I suppose, use an offset for the tool tip when cutting arcs. You would have to change tools to cut arcs in other directions, of course.
You could add the offsets in when calculating your offsets for the tool table, but this would be difficult to remember to add the tool tip offset on every cut. Perhaps the easiest wat would be to use T0101 for a lefthand crank tool, and then T01nn when using it to cut an arc and include the larger offset in a second offset slot.