Are tools designed or discovered?

Tools are designed for a specific task. However, are we creating them pre-eminently, or do we stumble upon them? It seems as though we discover at first something primitive that works. We then go through an iterative process where we get a better and better solution. Take, for instance, the light bulb. It took thousands of failed attempts before the first successful light bulb filament showed light from an electric source. The same can be said about fire. We discovered it, but it took us centuries or millennia to harness fire to its full potential.