Set inbound_workflow_id to bind incoming calls on this number to a specific agent — Menace Voice will register the inbound webhook with the provider and the response will include a provider_sync block reporting the result. Omit it to add the number for outbound use only.
The (provider, account_id, address) tuple must be globally unique across all Menace Voice organizations, since inbound dispatch keys on it. Attempting to add a number that another organization already owns returns 409.