Two impressions on the same site are not worth the same to a buyer. One reaches a known in-market shopper, the other an unknown visitor. The thing that tells them apart is a signal. The Signals Activation module is how agents discover and use those signals.
A signal in AdCP is an audience or contextual segment an agent can discover and activate against inventory: an in-market audience, a first-party segment, a contextual category. The buyer agent discovers what signals are available, then activates the ones that fit its goal so the buy targets them.
Key idea
This is the same lever you learned in Track D under a new name. Identity raises match rate, match rate raises bid density and CPM. Signals do the same job for agents: better signals mean more relevant impressions, which buyers will pay more for.
For a publisher, exposing a quality first-party audience as a signal is a way to earn more from the same inventory, because an agent can now buy it on purpose rather than by accident. And the same rule as ever applies: consent gates it. A signal built from user data is only usable where the user’s consent allows.
Quick check
How is an AdCP signal like an identity match in header bidding?
Note
The IAB Tech Lab is building its own fast path for audience signals, called Agentic Audiences, which you will see in Track I. Same goal of relevance, a different mechanism.