"Most important tool" depends on what you mean by "important". For TFA, it means the environment where most of the thinking is done. So it's a legitimate claim.

"Most important tool" depends on what you mean by "important". For TFA, it means the environment where most of the thinking is done. So it's a legitimate claim. If you want to restrict "important" to the most critical link in the development chain, I suppose you would have to choose the compiler.