If your onboarding flow feels clunky and your product leaves people scratching their heads, no agency on earth can polish that turd. So let's just assume those bits are sorted.
the real tell is who actually runs the account. Demand to meet the person doing the day-to-day grind. if they can look you in the eye and explain exactly when the AI nailed it versus when it hallucinated nonsense, you're holding gold.
also business instincts matter more than most people admit. ask them something like "what's your go-to move for bumping conversion rate?" or "got any ideas for feeding qualified lead and purchase signals back to Google cleaner?" If the answer is vague or feels rehearsed, run. That's an one-way ticket to a slow bleed of budget and zero clarity.