Ad buying agency, chosen on published evidence

Agencies with a verified published price

How to appoint an ad buying agency

1. Establish whether the agency buys as your agent or as a principal. An agent buys inventory on your behalf and passes through the cost. A principal buys inventory itself and resells it to you at a margin it need not reveal. Both exist and both are legal, but they are entirely different purchases. Ask which model applies to each channel, and get the answer in writing.
2. Ask for full disclosure of fees, rebates and tech costs. Beyond the management fee there may be platform charges, data and audience fees, verification tools, and rebates or volume incentives the agency receives from vendors. Ask what the agency receives from any party other than you, and require that all of it appears in the contract.
3. Keep the platform accounts and the data in your name. Wherever the platform allows it, own the seat or the account and grant the agency access. It preserves your campaign history and audience data when the relationship ends, and it means the reporting you read comes from a system you can log into yourself rather than from a spreadsheet you receive.
4. Agree the reporting standard before the first flight. Define the metrics, the sources they come from and how often you receive raw log level or platform level data rather than a summary. Agree in advance what counts as a viewable impression and which verification vendor adjudicates, because those definitions decide what you are actually paying for.

Fee models, and what each one incentivises

The three common structures each pull in a different direction. A share of media spend is simple and widespread, and it rewards larger budgets rather than better outcomes, so it works best when your spend is stable and your goals are volume based. A flat retainer decouples the fee from the budget and suits advertisers who want the agency indifferent to how much is spent, though it needs a defined scope or it becomes an argument about hours. A performance fee tied to an outcome aligns interests properly but requires an attribution method both parties trust, which in upper funnel media is genuinely difficult. Many mature advertisers end up with a hybrid: a base fee covering the work, plus a modest performance component on a metric that can be measured cleanly.

Whichever model you choose, insist that media spend and agency compensation appear as separate lines on every invoice. That single requirement makes it possible to audit the relationship later and makes it obvious when a channel mix change is really a margin change. It also makes competitive comparison possible, since two agencies quoting a blended figure are not comparable at all.

The transparency questions that matter most

Ask where your money goes between your bank and the publisher. In programmatic buying the chain can include a demand side platform, an exchange, a supply side platform, data vendors and verification tools, each taking a cut, and the share of a budget that reaches the publisher varies considerably between setups. An agency that can explain its own chain, name the vendors and show what each one charges is demonstrating the competence you are hiring for. One that treats the question as impertinent is telling you the answer is uncomfortable.

Ask, too, about brand safety and about the claims in the creative. The Federal Trade Commission's online advertising and marketing guidance is clear that advertising must be truthful, substantiated and not misleading, and that material information must be disclosed clearly, with responsibility resting on the advertiser. That means claims written by your buying agency remain your legal problem, so agree who reviews copy, what substantiation is kept and where it is filed. It is a five minute conversation at the start of a relationship and an expensive one at the end of it.

Questions people actually ask

What is principal based buying and should I accept it?

It is when the agency buys inventory for itself and resells it to you at an undisclosed margin rather than passing through the cost. It is legal and sometimes cheaper, but you cannot audit it. If you accept it, do so knowingly, in writing, and for defined channels rather than by default.

Should the media budget flow through the agency?

For smaller programmes it usually does, for practical reasons. As spend grows, paying platforms directly where possible reduces credit risk and makes the true cost visible. Either way, require invoices that separate media, fees and third party tools, and reconcile them against platform reporting.

How do I audit an ad buying relationship?

Start with access: if you can log into the platforms yourself, most questions answer themselves. Then compare platform reported spend with agency invoices for the same period. For larger programmes, a periodic independent audit clause in the contract is standard and worth having from the first day.

What minimum spend do buying agencies expect?

It varies widely, and the published minimums in our index differ by more than an order of magnitude because they describe different channel mixes. Programmatic and connected television carry higher practical floors than search and social. Ask each candidate for their smallest workable engagement in writing.

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