-service_proxy_auth _global_ url *Note 4* A URL which, when `use_service_proxy` is true, is fetched once at the
- beginning of each session to authenticate the user and establish a session
- that encompasses a defined set of targets to search in.
+service_proxy_auth _global_ url If defined, this is the URL which, when `use_service_proxy` is true, is
+ fetched once at the beginning of each session to authenticate the user and
+ establish a session that encompasses a defined set of targets to search
+ in. When not defined, the URL is assembled from `auth_hostname` or
+ `pp2_hostname`, `sp_auth_path`, `sp_auth_query` and
+ `sp_auth_credentials`. See *Note 4* for details.