answering_policy_agent_not_ready
PUT /v1/phone-numbers/{number_id}/answering-policy names an agent in an ai step that does not belong to this tenant or has no published immutable version. Publish it first. Proved once per distinct agent the document names, at write time rather than at answer time: a draft must not become callable by being written into a menu branch, and a signed carrier callback is the wrong place to discover it. The same rule inbound_voice_agent_not_ready enforces for the single-agent agent route, under its own code because a policy document names many agents and the detail says which one failed.
Problem shape
Every non-2xx response is an RFC 9457 application/problem+json body. The type URI below is stable and machine-matchable, so branch on the final path segment (the code) and treat the status as redundant confirmation. See the error-handling guide.
{
"type": "https://docs.vocapable.com/errors/answering_policy_agent_not_ready",
"title": "…",
"status": 409,
"detail": "…",
"instance": "/v1/…"
}