identity
Who a call is from, carried all the way to the system that acts on it. Not who the agent is: who is asking.
Identity, in the agent context, is who a call is from: the verified name of the agent asking, carried with the request all the way to the system that acts on it, so the action gets attributed to the actual caller. It is not the same thing as an agent’s persona or role. A tool server can know exactly what it is and still have no idea who is talking to it, and most of mine did not until I made them care.
It earns a definition because identity is the thing middlemen lose. A gateway can verify a caller perfectly at its front door and then make the downstream call as itself, so every system behind it sees the gateway’s name instead of the caller’s. Security people have called that shape the confused deputy for almost forty years, and it happens with nothing misconfigured: every check passes, every log entry is real, and every attribution is wrong. The rule I keep: identity has to travel with the call, and a field the caller could have written for themselves is not identity, it is a claim.