Commerce Service Center uses the CSRInvokeAssembler servlet bean to make the request to the Assembler. The servlet bean parses the result from MDEX into a map of ContentItems keyed by type (Map<String.List<? ContentItem), which is included as an output parameter named contentItemMap. The raw search results are also returned as an output parameter. The contentItemMap is a convenience object used for quickly accessing specific content items in the result:

<dsp:droplet name="/atg/commerce/custsvc/catalog/endeca/InvokeAssembler">
  <dsp:param name="includePath" value="${endecaContentURI}"/>
  <dsp:oparam name="output">
    <dsp:getvalueof var="contentItemResult" param="contentItem"/>
    <dsp:getvalueof var="contentItemMap" param="contentItemMap"/>
  </dsp:oparam>
</dsp:droplet>