-@defun dbus-list-activatable-names
-This function returns the D-Bus service names, which can be activated.
-An activatable service is described in a service registration file.
-Under GNU/Linux, such files are located at
-@file{/usr/share/dbus-1/services/}.
+@defun dbus-list-activatable-names &optional bus
+This function returns the D-Bus service names, which can be activated
+for @var{bus}. It must be either the symbol @code{:system} (the
+default) or the symbol @code{:session}. An activatable service is
+described in a service registration file. Under GNU/Linux, such files
+are located at @file{/usr/share/dbus-1/system-services/} (for the
+@code{:system} bus) or @file{/usr/share/dbus-1/services/}. An
+activatable service is not necessarily registered at @var{bus} at already.