One: they bring you bad news first
A campaign underperformed, a mistake was made, a test failed. You hear it from them before you notice it, with what they are doing about it.
Providers who only report good news are spending their effort on your perception rather than your account. This is the single most reliable indicator on the list.
Two: they occasionally tell you to spend less
On a channel that is not working, in a month that is not worth it, on a test that failed. Advice that costs them revenue is the clearest evidence that the advice is real.
A provider who can only ever recommend more is selling, which is fine as long as you know that is what is happening.
Three: they know your business, not just your account
They know your slow month, your best offer, your capacity limits, who answers the phone, and which of your services actually makes money.
That context is what turns a vague request into correct execution, and it is what you are really buying from a service relationship.
Four: small things happen fast
A new offer live the same week. A budget shift the same day. A paused campaign within the hour.
Speed on small requests predicts everything about how the relationship handles genuinely urgent ones.
What is not a sign
Fast email replies, a pleasant account manager, polished decks, monthly calls, and attending your meetings.
All of it is agreeable and none of it predicts results. Judge the four above and treat the rest as pleasant.