Lately, the last few carves I have done, an odd bit request has shown up that is one I neither own nor ever added to a toolpath. It always shows up as part of the Vee part of an advanced vcarve. As I recall it’s happened when I’ve used both the 15° and 30° Vee bits.
In general, I would stay away from all three digit tool numbers (100 → 999). C3D hasn’t made any commitments on what tool numbers they want reserved for future use, but so far they have stuck to that range. The higher end (>700) doesn’t have any usage yet, but that was true of of the 600 range until the McFly came out.