A tool (10) for processing a workpiece in a processing machine has a connecting portion (11) which is at the machine side during operation and is preferably standardized, for connecting the tool with a numerically controlled machine tool (30), a plasma duct (44) for conducting a generated plasma, and an outlet portion (13) which is at the workpiece side during operation and is disposed at the end of the duct (44), and which comprises one or a plurality of outlets (22) for supplying the plasma to a workpiece surface.