Agencies Deploy AI Agents for Media Buying as In-Housing Threat Grows

Advertising agencies are accelerating their deployment of AI agents for media planning and buying, but the technology presents a double-edged sword: the same tools that could give agencies an edge also make it easier for brands to bring marketing operations in-house.

WPP recently announced tests of a media buying and planning agent for premium video inventory, while Dentsu has partnered with AI agent development firm Newton Research to enhance its analytics and media planning capabilities through Dentsu.connect. According to Caitlin Gelles, executive vice president of data technology and measurement at Dentsu, the partnership includes pilots for media-buying agents in the U.S. focused on transactional buying.

Why it matters

As AI agents lower the technical barriers to operating sophisticated media buying operations, agencies must demonstrate they can extract more value from these tools than clients could achieve independently. The World Federation of Advertisers reports that 71% of in-house teams are already implementing AI in marketing operations, with 93% planning further investment over the next 12-24 months. This shift could accelerate the long-running trend of brands bringing marketing functions in-house.

Efficiency gains drive adoption

Gelles said the primary goal of Dentsu's Newton partnership is time savings. "It takes hours to set up campaigns across systems... when you can store those nuances in a RAG database, or take how clients like to buy, and let AI find those efficiencies, that's where the value comes in," she explained.

Independent agency Butler/Till has been working with DoubleVerify to develop Claude-based agents that analyze media inventory quality and automatically adjust campaigns away from poor-quality ad space. Dutch agency group Dept launched Agent Studio, a consultancy service that lets clients rent the engineering workflows and architecture Dept uses to build its own AI agents.

Brands build their own capabilities

Hyundai has developed custom AI models and bidding agents with AI firm Chalice and its in-house media agency Canvas, using a containerized AI solution called OpenXBuild. When deployed to find inventory on OpenX's supply-side platform, the system reduced online video CPM rates by 67% and cut the cost per high-value action by 20% during pilot testing.

"We eliminated some not-great inventory that we might have purchased; we're focusing our investment on where it matters the most, and scaling it quicker," said Sean Gilpin, North America CMO of Hyundai. The company reinvested the savings back into its media budget.

Gilpin said future applications could extend across more of Hyundai's media evaluation. "To have this agent on my behalf, doing evaluation of every impression... that becomes a competitive advantage," he noted.

Speed as a differentiator

Dept implemented an e-commerce platform redesign for Swiss fitness brand Blackroll using AI agents built with Google's Gemini and Antigravity suites. Jonathan Whiteside, executive vice president of technology at Dept, said the redesign was completed 3.8 times faster than would have been possible without AI agents. Scott Zalaznik, CEO at Blackroll, said the company now uses AI agents for the majority of its e-commerce feature testing and development.

The details were first reported by Digiday during the Cannes Lions advertising festival.