Linked from
The 8 pages that link to Tool steel, each with the reason it gives.
TemperingRelated: Tempering tunes tool steel hardness while limiting brittleness in service.
VanadiumRelated: Vanadium is added to some tool steels to form hard, wear-resistant carbides.
PliersRelated: Pliers rely on durable steel jaws and cutting edges that resist deformation.
JackhammerRelated: Jackhammer bits require hard, wear-resistant steel to survive repeated blows.