An agent ID is the unique identifier of an RCS Business Messaging agent, in the form [email protected]. It appears in API requests and in the sender details a customer can view in the thread.
What the identifier is for
Every RBM agent has one, assigned when the agent is created in the RBM platform. The API uses it to address the agent that is sending, and a phone shows it in the conversation's sender information beside the brand name and logo, which is how a customer can confirm that the verified sender is who it says it is. The rbm.goog domain is Google's, so an ID in that form always means an agent that exists on Google's RBM platform, whichever provider operates it.
One agent, one brand, one use case
An agent ID is tied to a brand profile and a declared use case, transactional, promotional, OTP or multi-use. A business that wants separate senders for security alerts and marketing, which is the recommended practice for fraud alerts, registers two agents and gets two IDs. The verification process is per agent.
What it is not
It is not a phone number. RCS conversations are addressed by the agent ID, and the phone number only comes into play for the SMS fallback, which is sent from a registered 10DLC or toll-free number instead.