ve seen was preventable — not by hiring better, but byagreeing in writing what Ask them to commit to each line — and note the italics: every promise comes with a wayyoucan check it yourself in about two minutes, no tools, no trust required. Two more things worth writing down:What happens if a check fails— fix at no charge? Anything already broken in your source data— list it upfront so nobody argues about whose fault it was. If your provider hesitates to commit to a list like this, that hesitation is information.