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>
    <gadgets>
      <gadget id="move-sidebar" desc="Move the sidebar to the right side. Does not affect the collapsed sidebar on mobile devices." />
      <gadget id="exlinks" desc="Open external links in a new tab/window" />
      <gadget id="revisionjumper" desc="The revisionjumper creates an interface which allows you to jump between different revisions." />
      <gadget id="HotCat" desc="HotCat, easily add / remove / change a category on a page, with name suggestion" />
      <gadget id="ReferenceTooltips" desc="Reference Tooltips: Roll over any inline citation to see reference information, instead of having to jump away from the article text." />
    </gadgets>
  </query>
</api>