The essentials
- Criterion number one: can the agency measure? Ask how it installs the pixel and the conversions API, and how it reconciles its figures with GA4.
- 2026 pricing: 15 to 20% of media spend at an agency, a retainer of €800 to €2,500 a month for an SME, set-up fees of €1,000 to €3,000.
- Non-negotiable: the ad account, the pixel and the audiences belong to you; the agency accesses them as a partner.
- Warning sign: an agency that promises a ROAS or a cost per lead before seeing your data and your margin.
Social ads agencies all look alike on their websites: the same platform logos, the same growth promises, the same case studies. The difference comes down to four verifiable points: the ability to measure, the testing method, the transparency of the business model and the ownership of the assets. Here is how to check them before signing, with 2026 price ranges in France.
The four criteria that separate agencies
| Criterion | What to check | How to check it |
|---|---|---|
| Measurement | Installation of the pixel and the conversions API, reconciliation with GA4, attribution window used | Ask for a screenshot of an anonymised client report showing platform and GA4 side by side |
| Testing method | Rate of creative renewal, audience testing protocol, stop rules | Ask how many creatives are produced per month per client, and who produces them |
| Business model | Percentage of media, retainer or a mix; what is included (creatives, pages, reporting) | Insist on a detailed quote line by line, with the number of monthly hours |
| Ownership of assets | Ad account, pixel, audiences and creatives stay with the advertiser | Read the contract; refuse any campaign run from the agency's account |
Measurement comes first because an agency that steers on Meta's or LinkedIn's figures alone optimises towards conversions overstated by 20 to 50%. The foundations of a reliable measurement set-up are described in conversion tracking in SMA and in GA4 and SMA.
2026 rates and what they include
| Model | 2026 range | Suits | Point to watch |
|---|---|---|---|
| Percentage of media | 15 to 20%, tapering above €20,000 a month | Budgets above €5,000 a month | Encourages spending more; insist on a floor and a ceiling |
| Monthly retainer | €800 to €2,500 for an SME, €3,000 to €8,000 for a multi-country account | Budgets of €1,500 to €10,000 a month | Check the number of hours and creatives included |
| Set-up fees | €1,000 to €3,000 | Any new account | Must cover the audit, the measurement and the initial structure |
| Performance-based variable | 5 to 15% of the margin generated, on top of a reduced fixed fee | E-commerce with reliable measurement | Define precisely the conversion and the attribution counted |
An agency that accepts a media budget of €500 a month with €400 of fees is not doing its client a favour: the fees exceed what the media can return. The consistent budget thresholds are detailed in what budget to plan for SMA.
The questions to ask in meetings
- “How will you know that a conversion reported by Meta is real?” The expected answer mentions the conversions API, deduplication and GA4.
- “How many creatives do you produce per month, and who produces them?” Fewer than four a month on Meta or TikTok is not enough in 2026.
- “What rule makes you switch off a campaign?” A serious agency has a cost-per-conversion threshold and a minimum test duration.
- “Who manages my account day to day, and how many accounts does that person handle?” Beyond ten to fifteen accounts per person, monitoring becomes weekly at best.
- “What happens if we stop working together?” The access, the audiences and the creatives must stay in your possession, with no delay and no fee.
- “Show me a real client report.” A useful report fits on one page and comments on the gaps; reporting templates are described in a supplier's reporting.
The warning signs
- A promise with figures before the audit: a ROAS of 5 or a €10 lead announced without knowing your margin or your data.
- The agency's ad account: if the relationship ends, you lose the history, the pixel and the audiences.
- Reporting limited to impressions and clicks: it hides the absence of measured conversions.
- A 12-month commitment with no exit clause: three months' notice is enough in a balanced contract.
- The same set-up for every client: an agency that puts everyone on Meta with Advantage+ has not looked at your target; the comparison of platforms for B2B and B2C is covered in B2B vs B2C platforms.
Agency, freelance or in-house: the prior question
Choosing an agency assumes that the agency format is the right one. An experienced freelance suits a single-platform account with €1,500 to €8,000 of media a month; an agency becomes relevant above that, or when creative production and several platforms are involved; bringing it in-house makes sense from €15,000 to €20,000 of monthly media. The full comparison is in SMA: freelance or agency.
How a good selection process works
Consult three agencies, with the same written brief, stating the budget. Ask for a one- to two-page recommendation note rather than a 40-slide deck: the reasoning matters more than the layout. Check two client references by phone, asking about measurement and about responsiveness. Start with a three-month period with written objectives and a mid-term review.
How GreenRed helps
Rather than juggling several tools, GreenRed's SMO / SMA social media module brings these metrics together in a single dashboard, compares them over time and tells you which actions come first. You can try it free, with no card, from the Pricing.
Frequently asked questions
Can a generalist agency handle social ads as well as a specialist agency?
Yes, if it has a dedicated team with people who manage Meta, LinkedIn or TikTok accounts day to day. The risk with a generalist agency is the account handed to an all-rounder who also handles SEO and emailing. Ask how many social ads accounts it manages in-house.
Should you insist on Meta or LinkedIn certifications?
They attest to a knowledge of the interfaces, not to results. A Meta Business Partner badge indicates a volume of spend managed and access to support, which is useful. Verifiable client references and the quality of the reasoning in meetings remain more reliable criteria than certifications.
How long before judging an agency?
Three months for a lead generation campaign, with a review at six weeks. The first month is for measuring and testing; the second for stabilising; the third for optimising. Judging on one month means judging the learning phase, and waiting six months with no interim review is expensive.
What should the contract contain?
Ownership of the accounts, the pixel, the audiences and the creatives; the list of services included with a volume (hours, creatives); the reporting arrangements; a termination notice of one to three months; the absence of any clause preventing you from contacting the platforms directly; and personal data processing compliant with the GDPR.