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"?>
    <alltransclusions gatcontinue="ConfigImageHeader|18" />
      <page pageid="1" ns="0" title="Main Page" />
      <page pageid="14" ns="0" title="Main Page/Multiple RGB Cameras" />
      <page pageid="18" ns="0" title="Main Page/Multiple Depth Sensors" />
      <page pageid="19" ns="0" title="Main Page/Single Depth Sensor" />
      <page pageid="27" ns="0" title="Main Page/Common Features" />
      <page pageid="31" ns="0" title="Main Page/Pro Edition Exclusive Features" />
      <page pageid="519" ns="0" title="Main Page/Special Features in Basic and Pro Editions" />