Is this how to send json data?

I got no errors but I am unable to retrieve the data after I've sent it.

<cfhttp url="https://app.kb.com/api/head/comment.json" method="post" timeout="15" throwonerror="true" >

  <cfhttpparam type="url" name="_authbykey" value="56ec1f1232131c78636142d6">

     <cfhttpparam type="url" name="project_id" value="55c4ffd123131c527e294fe6">

     <cfhttpparam type="url" name="article_id" value="#artID#">

     <cfhttpparam type="url" name="content" value="#serializeJSON(form.message)#" />

     <cfhttpparam type="url" name="public_name" value="#serializeJSON(form.name)#" />

     <cfhttpparam type="url" name="public_email" value="#serializeJSON(form.mailfrom)#" />

</cfhttp>

I've tried the serializeJSON() but I'm not sure if that's all I need. I've read this thread at StackOverFlow and it seemed that I've to build the string myself. However, that thread was about two years ago. I wonder if there is any changes in ColdFusion that does not require me to build the string myself.