Written specification
A documented behavior specification exists prior to development, defining intended use cases, in-scope and out-of-scope inputs, authorized tools, data scope, and conditions under which the agent must refuse or escalate.
The specification captures the agent's intended behavior in language a non-engineer can read and a tester can verify. It includes positive behavior (what the agent should do), negative behavior (what it should never do), escalation behavior (when and to whom it should hand off), and the conditions under which the specification itself should be revisited.
Specification exists for every production agent, is version-controlled, is current within an explicit time window, and is referenced by the operating runbook.