To clarify, instead of intent a better word may be knowledge. If the supplier knows that the user is going to use the tool for harm but gives the tool to the user anyway, then the supplier shares culpability. If the supplier does not (reasonably) know, either through invincible ignorance (the supplier could not reasonably know) or the user’s deception (lying to the supplier), then the supplier is not culpable.

I would say the supplier is culpable if the tool supplied is made for the purpose of the harm intended or if the supplier is giving the tool to the person who does the harm with the explicit intent for that person to use it for that harm. For example, giving someone an AK-47 to shoot someone or a handgun/rifle with the intent that the user shoot someone with it. If the supplier gives someone a tool to use for one legit purpose but the user uses it for a harmful purpose instead, I don’t think you can blame the supplier for that. For example, giving someone a knife to cut food with, and then the user goes and stabs someone with it instead. That’s entirely on the user and nobody else.