You are looking at the HTML representation of the XML format.
HTML is good for debugging, but is unsuitable for application use.
Specify the format parameter to change the output format.
To see the non HTML representation of the XML format, set format=xml.
See the complete documentation, or API help for more information. 
<?xml version="1.0"?>
<api>
  <warnings>
    <main xml:space="preserve">Unrecognized parameter: '*'</main>
  </warnings>
  <query>
    <exturlusage>
      <eu pageid="208" ns="0" title="Hjálp:Leiðbeiningar" url="http://www.mediawiki.org/wiki/Help:Contents" />
      <eu pageid="1416" ns="0" title="Bootcamp Jan 2011" url="http://www.mediawiki.org/wiki/Help:Contents" />
      <eu pageid="3511" ns="0" title="Bootcamp Dec 2011" url="http://www.mediawiki.org/wiki/Help:Contents" />
      <eu pageid="4678" ns="0" title="Bootcamp Oct 2013" url="http://www.mediawiki.org/wiki/Help:Contents" />
      <eu pageid="4685" ns="0" title="Bootcamp Nov 2013" url="http://www.mediawiki.org/wiki/Help:Contents" />
      <eu pageid="5001" ns="0" title="Bootcamp Aug 2014" url="http://www.mediawiki.org/wiki/Help:Contents" />
      <eu pageid="1251" ns="0" title="20100716" url="http://www.mediawiki.org/wiki/Help:Formatting" />
      <eu pageid="232" ns="4" title="Fab Lab Wiki - by NMÍ Kvikan:Community Portal" url="http://www.mediawiki.org/wiki/Manual:$wgSpamRegex" />
      <eu pageid="5472" ns="0" title="Whoispage" url="http://www.mediawiki.org/wiki/Project:Bureaucrats" />
    </exturlusage>
  </query>
</api>