The description element in the returned RSS xml is constructed using the view as specified in the URL, when no view is specified, the default no-name view is used.

To change this format, specify the sysparm_view parameter on the URL. For example, the following request will return the incidents list. However the result will be restricted to only the fields available in the ess view:
 https://<instance name>.service-now.com/incident.do?sysparm_query=priority=1&sysparm_view=ess&RSS
Additionally, the RSS item title can be modified using the sysparm_title_view URL parameter. When specified, the item title will be constructed using the fields specified in the view. For example:
https://<instance name>.service-now.com/incident.do?sysparm_query=priority=1&sysparm_view=ess&sysparm_title_view=rss_title&RSS