Agent registry

An agent registry is a directory of AI agents and MCP servers that lists who runs each one, where to reach it, which tools it offers and which checks it has passed.

As media buying moves to software agents, a buyer's agent needs to know that a seller's agent is real and belongs to the company it claims. A registry plays the role that ads.txt and sellers.json play for supply: a public place to check identity before trading. The IAB Tech Lab runs the Agent and MCP Server Registry. Anyone can browse it without logging in, and visitors can request a short-lived credential to query it over REST or MCP. Registering an agent requires a Tools Portal account (IAB Tech Lab registry, read 9 November 2026).

Each entry shows the operator, the protocol, the endpoint and the tools the agent exposes, with short descriptions. A listing is not a certification. Buyers should still check the operator's domain, test the endpoint and read the tool descriptions before an agent spends money.

Example: On 9 November 2026 the registry's browse page listed 53 entries: 52 MCP servers and 1 A2A agent. One seller entry exposed tools named get_products, list_creative_formats, sync_creatives and create_media_buy, which a buying agent can call in that order to plan and book a campaign.

Related terms: MCP, A2A (Agent2Agent), agentic advertising, AAMP, AdCP, sellers.json.

Authoritative source: IAB Tech Lab, Agent and MCP Server Registry (registry.iabtechlab.ai, read 9 November 2026).

Read the full guide: IAB Tech Lab Agent Registry explained.