A portfolio shows someone at their best. What you want to know is how they work when things go badly, and that appears on no website.
The reference that counts
Call two clients the agency did not put forward itself. You will find them on the factsheets, in the trade press, or simply by asking who still works for them. Then ask one question: what went wrong, and what happened next?
Every relationship longer than a year has had a moment where something broke. A client saying everything was always perfect either had a short relationship or has no wish to discuss it. The answer to that single question tells you more than ten slides of case studies.
Three signals in the work itself
- Different work for different clients. An agency that makes five brands look alike is selling its own taste rather than your positioning.
- Work that names a problem. Ask what the assignment was for every case. Anyone who cannot answer that easily made the campaign without owning it.
- Work that is still alive. A campaign that ran for three years says more than one that won an award and then vanished.
The number to know alongside
Median staff turnover in the Belgian agency market was 34.6 percent of headcount in financial year 2024. So about a third of the people change every year, and at a quarter of agencies more than two in three walk out the door.
That means "is this agency good" is a question about a team that will be partly different next year. So ask how long the people on your account have been there, and what happens if the most important of them leaves.
What else you can check for free
The filed annual accounts say whether the agency covers its own operation, and the factsheets put those figures next to the market medians. See how to know whether an agency is financially healthy and is an agency reliable to work with.