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>
    <tags>
      <tag name="blanking" displayname="Blanking" description="Blanking a page or section of content." hitcount="7" />
      <tag name="mobile edit" displayname="Mobile edit" description="[[Edit]] made from [[:Category:Mobile phones|mobile]] device such as a [[:Category:Smartphone|smartphone]] or [[:Category:Tablet|tablet]] (accessed via [[:Category:Web|web]] or [[:Category:Applications|app]])." hitcount="4856" />
      <tag name="mobile web edit" displayname="Mobile web edit" description="[[Edit]] made from [[:Category:Mobile phones|mobile]] [[:Category:Web|website]]." hitcount="4856" />
      <tag name="shouting" displayname="Shouting" description="Writing in all CAPITAL letters." hitcount="0" />
      <tag name="repeating characters" displayname="Repeating characters" description="The same character unnecessarily repeated multiple times; very likely [[vandal]]ism, or the cat stood on your keyboard." hitcount="0" />
    </tags>
  </query>
</api>