When the feed.http-hook is fired, the HTTP script only gets barebones information. Would be nice to have a storyURI and objectURI (and whatever else is easily accessible and equally useful).
Sample POST is below:
Array ( [storyID] => 719 [storyType] => PhabricatorApplicationTransactionFeedStory [storyData] => Array ( [objectPHID] => PHID-DREV-3y5ngrx26wfopfrbkyew [transactionPHIDs] => Array (  => PHID-XACT-DREV-brw7rovwpvcurdh  => PHID-XACT-DREV-prmajp3rypmbtri ) ) [storyAuthorPHID] => PHID-USER-s7hj4zduwubpc57fsce6 [storyText] => user43215 created D109: - fixed some stuff. [epoch] => 1406561703 )