<http://schema.org/description>
"Update: It transpires that 'Check out this idea' isn't actually a feature that has been implemented or tested by Facebook and is not part of Sponsored Stories. The custom action is ..."^^<http://www.w3.org/2001/XMLSchema#string>
<http://thenextweb.com/facebook/2011/12/27/facebook-starts-testing-check-out-this-idea-call-to-action-on-sponsored-stories/>