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="ColorTitleNav" />
  </query-continue>
  <query>
    <pages>
      <page ns="10" title="Template:Boite utilisateur" missing="" />
      <page pageid="2" ns="10" title="Template:Boxlayout1" />
      <page pageid="978" ns="10" title="Template:Building-Hut Data" />
      <page pageid="777" ns="10" title="Template:Building Data" />
      <page pageid="693" ns="10" title="Template:Building levels" />
      <page pageid="1127" ns="10" title="Template:Bunker Guild" />
      <page pageid="665" ns="10" title="Template:Clear" />
      <page pageid="32" ns="10" title="Template:ColorBackground" />
      <page pageid="33" ns="10" title="Template:ColorBorder" />
      <page pageid="34" ns="10" title="Template:ColorTitleBox" />
    </pages>
  </query>
</api>