Why it matters
Brands lose trust at the seams: playful on social, robotic in invoices, legalistic when apologising. Buyers experience that as not knowing who they're dealing with. Tone guidance keeps the personality recognisable exactly when the stakes make it hardest.
How it works
Good tone guidance maps the moments that matter (selling, onboarding, billing, bad news) and shows how the voice bends in each: more energy here, more restraint there, never sarcasm in a complaint. Side-by-side examples beat adjectives; "professional but friendly" has never helped anyone write.
What to do about it
Find your three highest-stakes message types and write a model example of each in your voice. Those three artefacts will quietly train everyone who writes after you.