How to brief a performance marketing agency you can actually measure

Most agency relationships fail in the brief, months before anyone notices. If the brief does not define the baseline, the peer set and the failure condition, no report the agency writes afterwards can be checked.

A brief is usually written as a description of the client and a list of things the client would like. It is rarely written as a measurement contract. That is why, a year in, the client cannot say whether the agency worked and the agency cannot prove that it did. Both sides are arguing about a number nobody defined.

Five things to put in the brief

1. The baseline, dated

Where the brand stands today, across the dimensions the work is meant to move, measured in a way that can be repeated. If you do not have this, make the first deliverable an audit that produces it, and make the audit a separate, paid piece of work so the agency has no incentive to shade it.

2. The peer set

Name the four to six companies the brand actually competes with for the buyer's attention, and require that every metric be reported against them. Absolute numbers flatter everyone. Relative numbers tell the truth.

3. The constraint, not the channel

Brief the problem: demand is flat in one segment, conversion drops at pricing, the brand is invisible in AI answers. Do not brief the channel. An agency briefed on "run paid social" will run paid social whether or not it is the constraint. An agency briefed on the constraint has to argue for its recommendation with evidence.

4. The evidence standard

State that every reported figure must carry its source and its evidence tier: measured, modeled or inferred. State that platform-attributed conversions will be reported as the platform's claim, in their own column. This one paragraph changes the quality of every report you will receive.

5. The failure condition

What result, by what date, would show that the approach is not working and should change. Write it down before the work starts. An agency that will not agree to a failure condition is telling you something.

Three things to leave out

• A required channel mix. That is the agency's job to recommend and yours to interrogate.
• Vanity targets. Followers, impressions and sessions are inputs. Brief outcomes.
• A twelve-month scope on day one. Brief the audit and the first ninety days. Renew on evidence.

The one question

At the pitch, ask: show me a client where your recommendation was to spend less, and what happened. A partner has an answer. A vendor changes the subject. The reason this question works is that it tests whether the agency's process can produce an answer the agency does not profit from. Everything else in the brief is there to make sure it keeps doing so once the contract is signed.

What a good response looks like

It pushes back on the brief. It asks for the baseline or proposes to build one. It names the peer set and may disagree with yours. It ranks the possible work by expected movement and says which lines are uncertain. It states the failure condition in its own words. And it is shorter than you expected, because most of what usually fills an agency response is there to avoid being pinned down.