For several months, agencies across the ad sector have been developing AI agents that function using the AdCP or MCP protocols as different companies pursue competing visions of AI-assisted media planning and buying. Those efforts are now bearing fruit.

Last week, Comcast-owned CTV ad tech firm FreeWheel unveiled an MCP server designed to provide an “infrastructure layer” for agencies including launch partners, media shop PMG and full-service agency Brkthru. Digiday previously reported on Butler/Till’s lead-up to the Geloso tests in December, prior to their kick-off.

“This was an early test, a successful one, and a clear proof point that agentic buying can drive real, measurable performance,” said Gina Whelehan, group director, strategic partnerships, Butler/Till.

‘Cost efficiencies… without trading off a single thing’

Butler/Till’s test campaign ran in two distinct flights between December 2025 and January, across a range of CTV, online and mobile app publishers that includes Samsung, Paramount, Vizio and Tubi. 

According to results seen by Digiday, the test delivered an 82% reduction in supply chain costs (particularly demand-side platform, or DSP, tech fees) translating into a higher proportion of working media made available for the campaign’s budget. Those savings led to a 40% lift in impressions delivered and a 30% fall in cost-per-thousand (CPM) rates. “We saw meaningful cost efficiencies, impression over‑delivery, and high‑quality inventory without trading off a single thing,” said Whelehan, who declined to reveal the exact budget deployed.

In basic terms, the process used in the test consisted of a series of messages pinged back and forth between the agency’s Claude agent, and Pubmatic’s own agentic systems:

• An agent built using Anthropic’s Claude LLM, communicated what kinds of ads and which audiences to target in Pubmatic’s AgenticOS system, based on a client brief written by human staff.
• A Pubmatic agent retrieved curated ad inventory, which was then relayed back to the agency staff team for approval.
• Butler/Till’s agent confirmation was sent back to AgenticOS, and the remainder of the media purchase was handled by Pubmatic’s existing tech chain.

Harry Tong, director of sales engineering at Pubmatic, said the process could be “transformative,” because it enabled buyers to circumvent the programmatic supply chain without requiring expert knowledge of alternative paths. “The agent is not just the equivalent of an expert user… It can just absorb more information with less bias and provide significantly better recommendations,” said Tong.

Butler/Till recorded an average video completion rate (VCR) of 98%. An independent audit of the test by verification firm Jounce found an MFA rate of less than 1%, while 80% of the inventory used in the campaign was rated higher than DoubleVerify’s typical benchmark.

Whelehan said the test was principally aimed at providing a proof of concept for agentic media buying. “Does this actually work? Can we effectively get a campaign in market, and it runs, and it scales?” were the questions she and the team were looking to answer.

Eliminating DSP fees, she said, was a secondary benefit. “It was on our radar that we might see efficiencies there, but not necessarily a target,” she said.

Shaving down hours and minutes in the early phases of setting up a campaign was another goal. Tong said Pubmatic’s tests led to a 98% reduction in the time taken to set up a campaign for a client.

Though less flashy than reducing fee costs, condensing campaign setup times could provide a meaningful improvement for buyers. “Everyone under appreciates how much time is [spent] in setting things up,” noted ad tech consultant Jonathan D’Souza-Rauto.

AdCP and MCP

Whelehan said that Butler/Till is “actively talking to other SSP partners” ahead of further agentic tests, as well as companies like Scope3. And Pubmatic is running tests with “upwards of 10” agency partners, according to Tong. He declined to reveal which other agencies he’s working with.

Per comments made by Omnicom tech boss Paolo Yuvienco at an event for investors held last week, the holding company’s media agencies are also experimenting with similar tools. “We’ve done some experimentation already with actual media buys across some of those publishers with direct connections via agents,” said Yuvienco.

But AdCP is not the only agentic horse agencies are betting on. FreeWheel last week went public with its MCP Server, a system intended to support media planning agents by providing API access to the company’s own technology and that of its own partners.

Jeff Ellin, vp, product architecture at FreeWheel, said it was intended to reduce the need for agencies to develop as much of the AI architecture required for agents to communicate with other systems, while making FreeWheel an attractive means for agentic systems to access streaming inventory. 

Media agency PMG has been using the tech internally since December to hasten campaign set up for CTV and streaming buys, but not to execute media investments, said Ellin.

‘Those that add value will remain’

Agentic media buying remains very much in its infancy. But observers and practitioners wonder where the ability to cut down on programmatic middlemen and staff hours could eventually lead. By introducing clients to the idea that more of their work can be automated away — delegated to a few lines of code — are agencies like Butler/Till playing with fire?

Whelehan noted that the reins are still held by the agency’s human staff, checkpoints at which they added intrinsic value. “There were checks and balances throughout,” she said. But she also said she believes the wind is already blowing in the direction of automation. “I think it’s just going to change the way we service their business, where our attention is.”

Similar questions can be levelled at Butler/Till’s test partner Pubmatic. If DSPs can be automated out of the process, what’s to stop a brand or agency buyer’s AI agent going around an SSP and straight to a publisher? 

Forrester analyst Evelyn Mitchell-Wolf told Digiday that vendors like Pubmatic will increasingly have to compete on the quality underpinning their systems and customer service, rather than situational advantage, if they’re to retain a place in this truncated supply queue.

“That includes explainability, it includes transparency and trust building because we’re still in the growing pains of this whole thing,” said Mitchell-Wolf.

“You need to compress the fees within the supply chain. We think that’s what agentic solves,” Tong concluded. “Those that add value will remain.”