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>
  <query-continue>
    <alltransclusions gatcontinue="Centershot|436" />
  </query-continue>
  <query>
    <pages>
      <page pageid="35" ns="3" title="Benutzer Diskussion:Haensgen" />
      <page pageid="289" ns="0" title="DE:HTSWECO Installation" />
      <page pageid="328" ns="0" title="DE:HTS45LS Installation" />
      <page pageid="378" ns="8" title="MediaWiki:Gadget-Extra-Editbuttons.js" />
      <page pageid="398" ns="0" title="DE:HTS45 Installation" />
      <page pageid="403" ns="0" title="DE:HTS45 Uminstallation" />
      <page pageid="409" ns="0" title="DE:HTS40 Upgrade" />
      <page pageid="413" ns="0" title="EMS" />
      <page pageid="416" ns="1" title="Diskussion:EMS" />
    </pages>
  </query>
</api>