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>
    <allfileusages gafcontinue="Gnome-nettool.jpg" />
  </query-continue>
  <query>
    <pages>
      <page ns="6" title="File:Boom.svg" missing="" />
      <page ns="6" title="File:Clommunity-logo.png" missing="" />
      <page ns="6" title="File:Cloudy-home.png" missing="" />
      <page ns="6" title="File:Cnml1.png" missing="" />
      <page ns="6" title="File:Cnml2.png" missing="" />
      <page ns="6" title="File:Cnml detail.png" missing="" />
      <page ns="6" title="File:Cnml explorer1.png" missing="" />
      <page ns="6" title="File:Cnml explorer2.png" missing="" />
      <page ns="6" title="File:Cnml nodes.png" missing="" />
      <page ns="6" title="File:Cnml zones.png" missing="" />
    </pages>
  </query>
</api>