The choice happens implicitly rather than explicitly. If Claude tries an approach and hits a wall, it'll try a different approach. If an API call keeps not working, it'll choose a different API. It a tool is broken, it'll use something else. If it can't find docs nor read the code, it'll try to implement functionality from scratch. If you give it messy tools with confusing docs, you'll notice Claude not calling them as you'd expect, and instead trying something simpler instead.