What did I do wrong?

I created a new tool but MasterCam 6 does not distinguish the difference between the new tool and an existing similar one, when both tools are the same type. For example, the new tool is a down-cut 1/8” bit. The existing tool is an up-cut 1/8” bit. Both tools are “straight” type. Each tool has a different name and number. Yet, if I already have a toolpath defined with one of the bits, and then select the other bit for a new toolpath, MasterCam will display a popup message that reads:

“A similar tool . . . already exists in tool list. Add another?”

This normally does not cause a problem with me (just a minor annoyance). But when using nesting operations, MasterCam does not sort the toolpaths by tool number since MasterCam considers all tools in the same type as the same. This causes me to manually sort the NC file if I want to use nesting toolpath. So I would really like to find my problem and what I am doing wrong.

Any suggestions?

Thanks,
Mike