You’re spending $5K-50K/month on ads. You’re thinking about hiring an agency. Every agency’s website says “we drive results” and shows cherry-picked case studies. How do you actually tell who’s good?
Here’s what to look for — and the red flags that should make you walk away.
The Question Most Agencies Can’t Answer
Ask this: “How do you know a conversion came from your ads versus organic or email?”
If they say “we look at the platform data” — that’s the wrong answer. Meta, Google, and TikTok all claim credit for the same conversions. A naive agency reports platform numbers as gospel, which means they’ll tell you your ROAS is 5x when it’s actually 3x because every platform double-counted the same purchases.
A good agency understands attribution:
- Which conversions are incremental (wouldn’t have happened without the ad)
- How to dedup cross-platform claims
- Why Google Ads and GA4 show different numbers (and which to trust when)
If they can’t explain this clearly, they’ll waste your budget and neither of you will know it.
The Five Things That Matter
1. Do They Own the Tracking Layer?
Most agencies set up Google Ads, create campaigns, and use the platform’s built-in conversion tracking. They never touch your analytics setup. When data is wrong — and it’s always wrong somewhere — they report the wrong numbers and optimize against the wrong signals.
What good looks like:
- Agency audits your GA4, GTM, and conversion tags before running ads
- They fix broken tracking as part of onboarding (not an upsell)
- They implement server-side tracking (CAPI, Enhanced Conversions)
- They can explain the difference between your Shopify revenue and what Meta reports
Red flag: Agency starts running campaigns before verifying that conversion tracking works.
2. How Do They Report ROAS?
Ask for a sample report. Look at the ROAS number. Then ask: “Is this platform-reported ROAS or blended ROAS?”
- Platform ROAS = Revenue reported by Google Ads / Ad spend. This is usually inflated (platform takes credit for organic/email conversions).
- Blended ROAS = Total store revenue / Total ad spend. This is the real number but includes revenue from all sources.
- Incremental ROAS = Revenue caused by ads / Ad spend. This is the hardest to measure and the most honest.
Most agencies report platform ROAS because it’s the highest number. If an agency proactively gives you blended or incremental numbers, they’re honest.
3. What’s Their Data Stack?
Agencies that are serious about performance have opinions about:
- Analytics: GA4 configuration, custom dimensions, audiences
- Tag Management: GTM, server-side GTM, or custom pixel implementations
- Attribution: How they compare platform data to actual revenue
- Consent: How they handle GDPR, CCPA, Consent Mode v2
Agencies that just use the Shopify admin and Meta Ads Manager are operating with one hand tied behind their back.
4. Fee Structure
| Model | Good Sign | Bad Sign |
|---|---|---|
| Flat fee + % of spend | Aligned incentives | % is above 15% |
| Flat fee only | Predictable costs | No skin in the game |
| % of spend only | Scales naturally | Incentive to spend more, not smarter |
| % of revenue | Maximum alignment | They’ll take credit for organic revenue |
| Performance only | Confidence | Usually a bait-and-switch |
The best structure for most ecommerce brands: flat fee + small % of spend (5-10%). This gives the agency predictable revenue while aligning their incentive with efficient spending.
Red flag: Long contracts (12+ months) with no performance exit clause.
5. Platform Expertise vs. Generalist
Some agencies specialize (Google only, Meta only). Others are full-service. Neither is inherently better, but ask:
- For Google Ads: Do they have Google Partner status? Do they manage Shopping, PMax, Search, and Display separately?
- For Meta: Can they explain when to use CBO vs ABO? Do they test creative systematically?
- For TikTok: Have they run TikTok campaigns specifically (not just boosted posts)?
If they claim expertise across 8+ platforms, ask for specific case studies on each. An agency that’s good at everything is usually great at nothing.
Red Flags
- “We need a 6-month runway before results” — You should see directional results in 30-60 days.
- “We manage 200+ clients” — At scale, your account gets junior talent. Ask who specifically manages your account.
- “We can’t share our strategy” — Secrecy is not strategy. You own your ad accounts and should see everything.
- “Platform data is the source of truth” — It’s not. Your ecommerce platform (Shopify, WooCommerce) is the revenue source of truth.
- “We don’t do tracking setup” — If they can’t verify the data they’re optimizing against, their optimizations are built on sand.
What to Ask in the First Meeting
- “Walk me through how you’d audit our current tracking setup.”
- “Show me a real report from a current client (anonymized). What metrics do you highlight and why?”
- “If Google Ads says 50 conversions but GA4 says 35, what do you do?”
- “How do you handle attribution when we’re running on Google, Meta, and email simultaneously?”
- “What happens if ROAS drops below target in month 2 — what’s your diagnostic process?”
If they fumble questions 3 or 4, they don’t understand measurement. And if you can’t measure, you can’t manage. For a deeper list of questions, see our companion guide: 12 questions to ask before hiring an ads agency.
Our Approach
We built our tracking infrastructure first — server-side CAPI, cross-platform attribution, verified conversion data. Then we built the agency on top of it. Every campaign we run is measured against data we verify ourselves, not data a platform self-reports.
$500/mo base + 5% of ad spend. No long contracts. Full transparency on every metric.
Start with a free tracking audit — we’ll show you exactly what your current agency (or setup) is missing before you commit to anything.