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>
    <pages>
      <page ns="10" title="Vorlage:Dokumentation" missing="" />
      <page pageid="3696" ns="10" title="Vorlage:Infobox Betreuung" />
      <page pageid="3558" ns="10" title="Vorlage:Infobox Download" />
      <page pageid="3626" ns="10" title="Vorlage:Infobox Gott" />
      <page pageid="3536" ns="10" title="Vorlage:Infobox Klasse" />
      <page pageid="3611" ns="10" title="Vorlage:Infobox Ort" />
      <page pageid="3535" ns="10" title="Vorlage:Infobox Rasse" />
      <page pageid="3531" ns="10" title="Vorlage:Infobox test" />
    </pages>
  </query>
</api>