An agency's team page is a snapshot and a marketing piece at the same time. The useful question is not who works there, but who will be on your account.
Where to look
IKAg's factsheets show per agency who is publicly findable, with their role. LinkedIn gives you the same with a date attached: you see who started recently and who left. The social balance sheet in the annual accounts gives the number, not the names, plus arrivals and departures for that year.
Line those three up and you have a reasonable picture: how many people, how stable, and who the key figures are.
The three questions that count
1. Who is on my account day to day? Ask for names and roles, not an org chart. And ask whether those people will be at the table next time.
2. How many other clients do those people carry? A strategist on nine accounts is a strategist you see twice a year. That may be enough, but at least you know.
3. Were these people in the pitch room? The classic gap between who presents and who works still exists, and it is the most predictable cause of disappointment in the first year.
Put it in writing
If particular people were decisive in your choice, put their names in the contract, with an agreement on what happens if they are replaced: who decides, with what notice, and whether you may refuse a replacement.
That is not distrust. With median staff turnover of 34.6 percent a year in this market it is simply realistic, and it makes the pitch promise checkable.
What a team page does not tell you
Who actually makes the work. Many agencies work with regular freelancers and subcontractors, and those rarely appear. That is not a problem, but you are entitled to know who touches your work, certainly when it contains sensitive information.
See also: how big an agency really is and what to ask in a first meeting.