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="Building_Data|472" />
  </query-continue>
  <query>
    <pages>
      <page pageid="1" ns="0" title="Main Page" />
      <page pageid="2" ns="10" title="Template:Boxlayout1" />
      <page pageid="7" ns="4" title="Xhodon:Community Portal" />
      <page pageid="8" ns="4" title="Xhodon:CategoryTree" />
      <page pageid="470" ns="0" title="Trollworld Mad Eye" />
      <page pageid="471" ns="0" title="Trollworld Breeding Pit" />
      <page pageid="890" ns="3" title="User talk:Bosskounet" />
      <page pageid="891" ns="2" title="User:Bosskounet" />
      <page pageid="974" ns="0" title="Dwarfworld Shaman Hut" />
      <page pageid="978" ns="10" title="Template:Building-Hut Data" />
    </pages>
  </query>
</api>