         
         if useDefaultTransformers
             {
-            configure
+            configure(description: "Siesta default response transformers")
                 {
                 $0.config.responseTransformers.add(JsonTransformer(), contentTypes: ["*/json", "*/*+json"])
                 $0.config.responseTransformers.add(TextTransformer(), contentTypes: ["text/*"])

            configurer: Configuration.Builder -> Void)
        {
        let entry = ConfigurationEntry(
            description: description ?? "custom",
            urlMatcher: urlMatcher,
            configurer: configurer)
        configurationEntries.append(entry)
        debugLog(.Configuration, ["Added", entry, "config"])
        }
    
    /**
      Signals that all resources need to recompute their configuration next time they need it.

    */
    public final func invalidateConfiguration()
        {
        if anyConfigSinceLastInvalidation
            { debugLog(.Configuration, ["Configurations need to be recomputed"]) }
        anyConfigSinceLastInvalidation = false
        
        configVersion++
        }

    private var anyConfigSinceLastInvalidation = false
    
    internal func configurationForResource(resource: Resource) -> Configuration
        {
        anyConfigSinceLastInvalidation = true
        debugLog(.Configuration, ["Computing configuration for", resource])
        let builder = Configuration.Builder()
        for entry in configurationEntries
            where entry.urlMatcher(resource.url!)
            {
            debugLog(.Configuration, ["Applying", entry, "to", resource])
            entry.configurer(builder)
            }
        return builder.config
