Exactly what it says in the title: the flay recipe for a Fletcher Impetus actually requires a toolsmith. This also means that the Toolsmith Impetus is unobtainable, since flaying a toolsmith just makes a Fletcher Impetus instead.

https://github.com/FallingColors/HexMod/blob/418184871b4e8f21435292ebbc3c48ab5a69634f/Forge/src/generated/resources/data/hexcasting/recipes/brainsweep/impetus_look.json