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="Documentation|1524" />
  </query-continue>
  <query>
    <pages>
      <page pageid="1387" ns="10" title="Template:Infobox" />
      <page pageid="1388" ns="0" title="Test2" />
      <page pageid="1394" ns="10" title="Template:Infobox camera" />
      <page pageid="1398" ns="0" title="Test country" />
      <page pageid="1615" ns="10" title="Template:Tiw" />
      <page pageid="2808" ns="0" title="Semester B Final Report 2014 - Cracking the Voynich code" />
      <page pageid="2963" ns="0" title="Cracking the Voynich Code 2015 - Final Report" />
      <page pageid="4401" ns="0" title="Semester B Final Report 2017 - Energy Storage Requirements for the SA Grid" />
      <page pageid="4423" ns="0" title="Semester A Progress Report 2017 - Energy Storage Requirements for the SA Grid" />
      <page pageid="4569" ns="0" title="Semester A Progress Report 2019 - Energy Storage Requirements for the SA Grid" />
    </pages>
  </query>
</api>