Originally meaning teacher's pet/suckup/brown-noser, this word has come to have a variety of other meanings now as well. The word tool in its latest and most common meaning originated from the USMA and USMA Prep School at West Point, New York (USMA=United States Military Academy)during the mid-late 1980s. One James Maynard Keenan attended West Point but dropped out eventually. He then created the popular band known as tool. An intersting factoid is that although keenan is now bald, in his school pictures from west point, he has what most call a "full head of hair." In some cases the word tool is used to mean dick.
Brian is a tool.
That band tool is good.