Contracts vary, but here if your employer tells you to do work ("document and deliver a tool that does X") and you refuse, here that's grounds for warning process and dismissal as a breach of contract.

His employer didn't tell him to do that.

You have to get used to acting within the grey area and playing politics. Your counterparty (your employer) certainly does. Every businessperson is good at it, or they wouldn't be successful.

In any transactional relationship - which employment is - when you want to do something, don't think: I can't do this because they wouldn't like it. Instead think: what are the likely consequences of doing this? Are they positive or negative for me, on net?