Using the LIKE operator with a wildcard using API v3's REST interface
the correct syntax is the one at the top:
&quot;first_name&quot;: {&quot;LIKE&quot;:&quot;hei%&quot;}
to work around the encoding issues (that might be tricky indeed), don't try to put all the params in the url (as http get) but use a http post (the api works with both)