There's a predictable moment, usually around month three, where a founder wants to redo everything, logo, name, colours, all of it. A one-page brief written on day one is what stops that spiral before it starts.

Tam Mckenzie
Brand & Business Consultant
It happens like clockwork. Somewhere around week ten or twelve, a founder messages me convinced the whole brand is wrong, wrong name, wrong colours, wrong tone, sometimes wrong logo they picked themselves three months earlier. It's rarely the brand. It's that nobody wrote down what the brand was supposed to do, so there's nothing to check the panic against.
The brief is genuinely one page, five sections, filled in before a single design decision gets made: the one sentence you want a customer to say about you unprompted, the two competitors you're most often confused with and the one difference that matters, the tone in three adjectives (and the three adjectives you're explicitly not), the non-negotiable visual constraint if you have one, and a single metric that would tell you the brand is working.
When the month-three doubt hits, and it will, because you'll have seen a hundred other brands by then and started comparing, you pull out the page. Nine times out of ten the brand hasn't drifted from the brief at all. What's drifted is your tolerance for looking unfinished. That's a founder problem, not a brand problem, and the page is what tells the difference.
The one line that saves the most time
"The three adjectives we are explicitly not." Founders skip this line constantly, and it's the one that stops a rebrand argument in under a minute six months later.