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="Infobox_service" />
  </query-continue>
  <query>
    <pages>
      <page ns="10" title="Template:Doc" missing="" />
      <page ns="10" title="Template:Fake" missing="" />
      <page ns="10" title="Template:Index" missing="" />
      <page ns="10" title="Template:Infobox" missing="" />
      <page ns="10" title="Template:Infobox Game Topic" missing="" />
      <page ns="10" title="Template:Infobox game" missing="" />
      <page ns="10" title="Template:Infobox game security" missing="" />
      <page ns="10" title="Template:Infobox game strategy" missing="" />
      <page ns="10" title="Template:Infobox image" missing="" />
      <page pageid="4132" ns="10" title="Template:Box Note" />
    </pages>
  </query>
</api>