Most agency evaluations focus on portfolios. The portfolio tells you what someone can build — not how they think when things get hard. The signal you actually want is in the conversation.
Ask how they have changed scope mid-project, what they cut and why. The answer reveals their judgement under pressure.
Ask how they handle bad ideas from the founder. A team that always agrees is not a partner. A team that pushes back usefully is.
Finally, ask what their delivery looks like in week three of a project. That is when ambition meets reality. The teams that ship cleanly at week three are the ones worth working with.