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>
    <pages>
      <page ns="0" title="API" missing="" />
      <page pageid="1" ns="0" title="Main Page">
        <revisions>
          <rev user="Andy" timestamp="2015-04-18T10:43:54Z" comment="/* User Guides */" contentformat="text/x-wiki" contentmodel="wikitext" xml:space="preserve">== User Guides ==

Check out the [[Basics of AVCMS|Basics of AVCMS article]] for help with some of the more complex AVCMS features.

== Developer ==

Check out the [[:Category:Developer|Developer Category]] for developer articles including template help.</rev>
        </revisions>
      </page>
    </pages>
  </query>
</api>