You are looking at the HTML representation of the XML format.
HTML is good for debugging, but probably is not suitable for your application.
See complete documentation, or API help for more information. 
<?xml version="1.0"?>
<api>
  <query>
    <pages>
      <page pageid="1" ns="0" title="Main Page">
        <revisions>
          <rev user="Farbs" comment="Whoa! First area got full very quickly. Moving the front page to calm things down a bit." />
        </revisions>
      </page>
    </pages>
    <general mainpage="Main Page" base="https://playpen.farbs.org/index.php?title=Main_Page" sitename="PlayPen" generator="MediaWiki 1.15.1" case="first-letter" rights="Public Domain" lang="en-gb" fallback8bitEncoding="windows-1252" writeapi="" timezone="UTC" timeoffset="0" />
  </query>
</api>