Yes of course...glad you mentioned ArcToolbox. The tool is the 1st one under the Features toolset:
Data Management Tools.tbx >> Features >> Add XY Coordinates
One very nice thing about this tool is that it automatically adds the fields (Point_x, Point_y, etc.) if you don't have them already in the attribute table - even adds the Z and M fields, if your dataset is so enabled. Even 'updates' these fields, if necessary, on subsequent runs of the tool (I just tested this).
Incidentally, if you already have X and Y fields defined and you wanted to maintain them, you can optionally use 'Calculate Geometry' from within ArcMap. (Right-click on the field header and select the appropriate value to calculate - have to run the field calculations separately, though.)