The IAB Phone Book for AI Agents.

Tim Rowe

Apr 20261 min read

The IAB Tech Lab's new Agent Registry doesn't come across as a flashy headline in today's streaming news cycle. But it could be the most consequential announcement of the year.

The Problem it Solves

DSPs, CDPs, measurement companies, identity resolution vendors — everyone is building agents. But an agent that nobody can find, verify, or trust is just expensive software sitting in a closet. The IAB registry is attempting to solve that problem with this announcement.

How it Started

The AAMP initiative provides reference implementations for creating advertising agents that adhere to existing standards, making it relatively straightforward to build one. The harder question has become what happens after you build it. How do partners find it? How do they know what it can actually do?

How it's Going

The registry intends to define the agents they've brought to market, categorize them, and provide details about their capabilities — spanning categories like Demand Side Platform, Identity Resolution, Measurement & Attribution, Customer Data Platform, and Consent Management.

The Trust Architecture

Every registered company gets tied to the IAB GPP ID, which includes IAB TCF Global Vendor List IDs for validation and IAB Tech Lab reviews each entry to ensure the necessary validation information is present.

The technical design choice is clever. The registry is itself an MCP server, so you are able to query it directly via Claude, Cursor, or any custom-built agent. In practical terms, this means an agent can ask the registry for a list of seller agents, buyer agents, or any other filtered view and get a structured, machine-readable answer.

Equativ and PubMatic are among the early registrants, which signals significant intent but the more interesting metric to track will be who registers in the next 90 days, and whether the buy side and sell side adopt it at comparable rates or one outpaces the other.

The roadmap includes agent scoring and ratings, geographic filtering, support for private/local deployments, and a verification mechanism for seller agents which is essentially an ads.txt equivalent for the agentic layer. That last item is the one to watch: the agentic layer. Ads.txt took years to reach meaningful adoption. Whether a parallel mechanism for agents moves faster will say a lot about how seriously the industry has learned from past infrastructure rollouts.