The stone shown in Figure B is a tool. It is a hand axe.
Figure A cannot be used as a tool because it has no sharp edge.
Figure B has been identified a tool because it has a sharp edge that could be used for various purposes. Hand axes have been the longest used stone tool made of flint. Hand axes were used for butchering animals, digging for water, chopping wood, throwing at preys and as a source for flake tools.