http webharvest tag not working with http-param parameters - http

Question

I am trying the below code in webharvest
<var-def name="url">https://www.athome.com/on/demandware.store/Sites-athome-Site/default/Stores-FindByZip?</var-def>
<var-def name="urlResult">
<html-to-xml>
<http url="${url}" method="GET" >
<http-param name="Content-Type">text/html;charset=UTF-8</http-param>
<http-param name="dwfrm_storelocator_countryCode">US</http-param>
<http-param name="dwfrm_storelocator_distanceUnit">mi</http-param>
<http-param name="dwfrm_storelocator_postalCode">07054</http-param>
<http-param name="dwfrm_storelocator_maxdistance">999999</http-param>
<http-param name="dwfrm_storelocator_findbyzip">Search</http-param>
</http>
</html-to-xml>
</var-def>
I get the error stating There was an error processing your request.
Screenshot of the error is Error Screenshot
But when i define the url with all the parameters, then i get the intended result
<var-def name="url"><template>https://www.athome.com/on/demandware.store /Sites-athome-Site/default/Stores-FindByZip?dwfrm_storelocator_countryCode=US&dwfrm_storelocator_distanceUnit=mi&dwfrm_storelocator_postalCode=07054&dwfrm_storelocator_maxdistance=999999&dwfrm_storelocator_findbyzip=Search</template></var-def>
<var-def name="urlResult">
<html-to-xml>
<http url="${url}" method="GET">
</http>
</html-to-xml>
</var-def>
Why we have this kind of differing behavior ?
Thank you !