Allowing HEAD request for custom API in Azure Mobile Services (with NodeJs backend)

Can anyone give me an example on adding permission to the HEAD HTTP request to a specific custom API in Azure Mobile Services? I want to create an endpoint for receiving a HEAD request t from thrid parties.

Thanks

Currently HEAD requests are not supported in API (or table) requests in the node.js runtime for Azure Mobile Services. Please consider creating a new feature request at http://feedback.azure.com/forums/216254-mobile-services.