Signal one: the trend, not the month
One month means nothing. Look at cost per booked job across six months. Flat is acceptable, down is good, up without an explanation you understand is the problem.
A provider doing real work can explain a rise in one sentence — competition, seasonality, a market shift — and tell you what they changed in response.
Signal two: what changed last month
Ask what specifically changed in your account in the last thirty days. Not strategy talk — changes. New creative, negatives added, budget shifted, geography adjusted, a test started.
Silence here is the most common sign of a set-and-forget account, which is by far the most frequent failure mode in this industry.
Signal three: whether they tell you bad news first
Good providers surface problems before you notice them, including their own mistakes. Providers who only report good news are managing you rather than the account.
The tell: has anyone there ever recommended you spend less on something?
Signal four: how fast something small gets done
Ask for one specific small change and time it. A new offer live, a budget shift, a paused campaign.
Hours or a day is healthy. A week means you are in a queue, and everything urgent will feel like this.
What is not a signal
A polished report. Fast replies to emails. A friendly account manager. Impressive-sounding platform jargon. Attending your meetings.
All pleasant, none predictive. Judge the four above and be indifferent to the rest.
One more quick check: ask when the ads themselves were last changed. If it has been more than two months, read why ad creative stops working.