This object, carried inside a TACACS+ server state-change notification, holds an optional text message the TACACS+ server itself provided, populated only when eriRouterTacacsServerReason indicates a serverError; otherwise it is a zero-length string. Admins read it for a human-readable explanation directly from the TACACS+ server when the outage was due to a server-reported error rather than a simple timeout. A trap carrying a nonzero-length message here, alongside a serverError reason, gives the admin the exact error text the TACACS+ server returned before going down.