Agencies do one of two fundamentally different jobs, and they’re priced similarly enough that people buy the wrong one constantly.
Job one: judgment. Working out who your buyer actually is, what’s broken, what to stop doing, and where the money should go. This is diagnosis, and it decides whether anything else works.
Job two: execution. Running the ads, building the pages, writing the content, sending the mail, producing the reports. Skilled, necessary, and completely dependent on job one being right.
Most disappointment comes from buying execution while expecting judgment. The work gets done competently, on time, exactly as scoped — against a strategy nobody ever produced. The account improves. The business doesn’t.
Disclosure: I run one. So here’s the question I’d want asked of me. What would you tell me not to do? Good strategy subtracts before it adds. An agency that only ever adds is selling activity — and activity is what gets priced by the hour.
Two more worth asking early: who actually does the work (the person in the pitch is frequently not the person on your account), and what they hold themselves accountable to — leads, or qualified opportunities your sales team would recognize as real.
Related: how do I choose a marketing agency? and how much does one cost?