How to choose your SEA agency in 2026

In short:

1. A good SEA agency is judged on its ability to manage profitability (acquisition cost, ROAS, margin), not on click volume.
2. Nine criteria make the difference, grouped into three families: technical expertise, business-driven management, and transparency and support.
3. Ad accounts and their history belong to the advertiser: an agency that refuses this access rules itself out.

Knowing how to choose your SEA agency directly determines the profitability of every euro invested in search engine advertising. Unlike organic search, paid search produces fast effects, in both directions: a well structured campaign can generate sales within the first weeks, while a poorly managed one burns through the budget without building anything. The choice of provider therefore rests on concrete criteria, which this guide reviews before detailing the questions to ask and the warning signs to look out for.

How to choose your SEA agency: start from your goals

A good SEA agency is chosen on three elements: its technical command of the platforms and of measurement, its ability to manage campaigns on business metrics rather than clicks, and its transparency on accounts, budget and results. That still requires having defined beforehand what advertising should bring in, and at what cost.

Before consulting agencies, the advertiser sets out quantified goals: volume of qualified leads, online revenue, maximum acceptable acquisition cost, expected profitability per campaign. These targets depend on the business model: an e-commerce site thinks in ROAS and margin per product, a B2B company in cost per qualified lead and contribution to the sales pipeline. SEA now covers far more than Google text ads: Shopping, Performance Max, YouTube, Demand Gen, Microsoft Ads, and now the ad formats of AI assistants.

The budget splits into two lines that must never be confused: the media budget, paid to the ad platforms, and the agency’s fees. It should be set at a realistic level for the length of a test, taking into account the calibration phase that follows any launch: automated bidding strategies need conversion data to learn, and a budget that is too small never gives them enough.

Expertise criteria: what an SEA agency must master

Official certifications, and their level

The Google Partner badge shows that an agency meets Google’s requirements for managed account performance, ad spend and team certifications. Premier Partner status goes further: Google reserves it for partners ranking in the top 3% performers of their country, based on an annual assessment. Equivalent programs exist on other platforms, such as Meta Business Partners or the Microsoft Advertising partner program. A certification does not guarantee the quality of campaign management, but its absence on an account with a significant budget should raise questions.

Command of platforms and formats

Search, Shopping, Performance Max, YouTube, Demand Gen, app campaigns: each format serves a different goal and follows its own rules. For an e-commerce site, the quality of the product feed drives a large part of Google Ads results on Shopping and Performance Max. For a B2B company, structuring Search campaigns around high value intents comes first. The agency must be able to explain why it recommends a given format for a given goal, instead of applying the same structure to all its clients.

Reliable conversion measurement

No optimization is better than the data that feeds it. Conversion tracking, feeding sales and qualified leads back from the CRM, consent management, server side tracking: a competent SEA agency audits measurement before touching bids. Bidding algorithms rely on these signals, and a miscounted conversion translates directly into badly spent budget.

Management criteria: a profitability-driven SEA agency

Business metrics rather than clicks

The difference between an agency that runs campaigns and one that understands a business model shows in the metrics it tracks. The first talks about clicks, click-through rate and Quality Score. The second talks about acquisition cost, ROAS, margin, customer lifetime value and genuinely qualified leads. It analyzes search terms one by one to steer budget toward profitable intents, and ties its optimizations to the advertiser’s revenue rather than to platform statistics.

A structure designed for algorithms

Today’s campaigns rely heavily on the ad platforms’ machine learning. A good agency structures accounts to support that learning: consolidated volumes, useful segmentation, no campaigns competing against each other, and business signals passed to the algorithms, such as the real value of conversions or first-party data. It also monitors competitive pressure using auction data, to balance aggressiveness and profitability by market segment.

The ability to say no

A results-driven agency knows how to turn down a channel it considers unprofitable, recommend cutting a campaign that underperforms or advise shifting part of the effort toward organic search when that makes more sense. This reflex is a good indicator of alignment: a fee indexed on media budget must never push toward spending more. On a new channel like ChatGPT Ads, open in France since 24 August 2026, this caution matters even more.

Transparency and support criteria

Ad accounts in the advertiser’s name

This is the most important rule and the most often neglected: Google Ads, Meta and analytics accounts must be created in the advertiser’s name, who then grants the agency access. If the contract ends, the history, audiences and conversion data remain the company’s property. An agency that runs campaigns from its own accounts creates a dependency that is hard to undo.

Readable pricing

Three models dominate the market: the monthly retainer, a percentage of ad spend and hybrid formulas that combine a fixed and a variable part. None is better in principle, but each must be explicit: what the fees cover, a clear separation from the media budget, the commitment period and exit conditions. A percentage of media budget deserves particular attention, since it gives the agency an interest in higher spend rather than in profitability.

Clear reporting and a dedicated contact

Reporting must be regular, readable and action oriented: evolution of acquisition cost, conversion rate and revenue, decisions taken and next optimizations. It is also worth knowing who follows the account day to day, how many other accounts that person handles and how often steering meetings take place. On a channel where performance shifts every week, the contact’s responsiveness matters as much as their expertise.

Before signing: questions to ask and warning signs

The grid below sums up the questions that make it possible to separate two SEA agencies in a single meeting.

Signals that should rule out an agency

• A guaranteed ROAS or cost per lead before any audit of the account and of measurement.
• Campaigns run from the agency’s own accounts, with no admin access for the advertiser.
• Reporting limited to clicks and impressions, with no link to revenue.
• Management fees taken out of the media budget without being itemized.
• The same campaign structure for every client, regardless of the business model.

datashake, an SEA agency built on these criteria

Among the agencies that meet these criteria, datashake first stands out for its origins: the group was founded in 2019 by two former members of Google’s European headquarters, as a paid media agency. It now reports more than 1,000 advertisers supported and 500 million euros in media budget managed. On certifications, datashake is among the 3% of French agencies certified Google Premier Partner, the highest level of the program, and among the few agencies selected for the Google Partners International Growth program.

On management, its method matches the criteria of this guide: analysis at search term level to concentrate budget on queries that generate revenue, margin or customer value, bidding strategies fed with business signals and first-party data, monitoring of competitive pressure and account structures built for algorithm learning. The agency has also developed its own tools: brand-saver, an algorithm that adjusts bids on brand keywords in real time depending on whether competitors appear in the results, and a proprietary comparison shopping service (CSS) for Shopping campaigns. The averages it reports across its clients are a 60% drop in cost per acquisition and ROAS multiplied by two.

On transparency and support, the agency works without long-term commitment and brings together in the same group SEA, social ads, SEO and GEO, tracking and data, CRM and an AI creative studio, which makes sound measurement and consistency across channels easier. On the organic side, the same principles apply when it comes to choosing your SEO agency. A free campaign audit is offered by datashake.

Frequently asked questions