Tone: conversational, not frivolous
The tone target is conversational but not casual: plain sentences, no jargon where a common word works, and no jokes in a document someone may read because something went wrong. Contractions are fine. Slang, exclamation marks, and rhetorical questions are not.
We also do not use “simply,” “just,” or “obviously” in instructions, since those words tell a confused reader that the confusion is their fault.