How to choose an ecommerce marketing agency: beyond the ROAS slide

Start with the store, not the shopping list.

More traffic. Better creative. A website that converts. All reasonable requests. They are also three different jobs, and the agency that is right for one may need a partner for another.

Before asking for a proposal, write down what has changed. Perhaps paid acquisition is growing while repeat purchases are flat. Perhaps shoppers reach product pages but cannot work out sizing. Perhaps stock shortages keep turning successful campaigns into expensive waiting lists. Give the agency the actual knot to untangle.

Share a recent trading period, the comparable seasonal period, major promotions and the products you can reliably fulfill. Separate new customers from returning customers where the data allows. If those records are incomplete, make discovery and measurement part of the scope rather than asking for a precise forecast from a blurry picture.

Compare four kinds of work.

Ask the agency which of these it will own, which it will advise on and which it expects your team to deliver. An honest boundary is useful. A proposal that assigns every dependency to “the client” deserves a conversation about whether your team has the capacity.

Give the revenue number a little context.

Here is a fictional example, not a Carbon client result. A campaign produces $20,000 in attributed order revenue on $5,000 of media spend: a reported 4× ROAS. If product costs, discounts, fulfillment, payment fees and expected returns leave $7,000 before advertising, the campaign leaves $2,000 after media and before agency fees and overhead.

That does not settle whether the campaign is a good investment. Repeat purchases, genuinely incremental orders and the business’s cash position matter too. It does show why a revenue multiple is only part of the buying decision. Ask which costs the proposed report will include and which it will leave out.

For a subscription or replenishment business, ask how repeat behavior is observed rather than assuming every new customer has the same future value. For a seasonal store, agree how promotions and stock availability will be annotated.

Ask for the story behind the case study.

A useful case study identifies the agency’s role, starting conditions, timeframe and outcome definition. Ask whether an improvement was measured across the store or attributed by one platform, whether spend changed and whether a promotion contributed. You are checking comparability, not asking someone to disclose a client’s confidential margin.

Give shortlisted teams the same short brief. Ask each to propose the first three decisions it would investigate, what evidence it needs and what it would postpone. This tests how the team thinks without demanding a free finished strategy.

For the measurement discussion, Google’s ecommerce event guidance distinguishes shopping actions such as product views, carts and purchases. Ask how your implementation records the journey, not simply whether GA4 is installed.

Make the commercial comparison fair.

Separate agency fees, media, creative production, development, apps and other third-party costs. Confirm the approval process, reporting access and what happens to accounts and creative when the engagement ends. Compare the same responsibilities across proposals before comparing the totals.

A first phase can be useful when the underlying data or storefront constraints are unclear. Ask what decision that phase will enable and what evidence will count as complete. A discovery phase with no defined output can become a very expensive introduction.

Carbon works on a project or retainer basis. Projects receive a custom quote based on needs and timing; retainers start as low as $5,000/month. That starting point does not price every service or include every production cost. See our engagement and pricing guide and ask for a scope that fits the job.

A few questions before you brief the crew.

Should we hire one agency for everything?

Only if the proposed team can cover the work and coordinate the dependencies. A specialist media partner can fit a strong internal ecommerce team; a broader partner can help when creative, shopping experience and acquisition need to change together.

Do we need a redesign before hiring an agency?

Not automatically. Identify whether the barrier is a specific journey, product information, measurement or the platform itself. Our ecommerce redesign guide helps separate a focused improvement from a larger rebuild.