Must-have requirement
A skill the hire needs on day one, because the core work depends on it. Most job descriptions have three to five real ones.
What it tells you about a developer
A candidate strong on the true must-haves who matches only some nice-to-haves is submittable. Name the gap and pair it with evidence that they pick up adjacent tools fast.
Must-haves are usually the primary programming language, the engineering discipline, and the problem domain. Everything else on the list is typically negotiable, even when it sits under a heading that says required. The intake meeting exists largely to find which lines are genuine must-haves.