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>
    <search>
      <p ns="0" title="Mupen64Plus v2.0 Core Front-End" snippet="...writable.  Each parameter&amp;#039;s value is held in a single 32-bit integer.  The &lt;span class=&#039;searchmatch&#039;&gt;meaning&lt;/span&gt; of this integer is given in the Parameter Encoding column. See the table be&#10;" size="21084" wordcount="3597" timestamp="2020-06-28T17:55:59Z" />
    </search>
  </query>
</api>