Improve sort() documentation

README.md

@@ -636,7 +636,7 @@ Extensions Supported
 
     * Additional ImapConnection functions
 
-      * **sort**(<_array_>sortCriteria, <_array_>searchCriteria, <_function_>callback) - _(void)_ - Performs a sorted search(). Valid sortCriteria are (reverse sorting of individual criteria is done by prefixing the criteria with '-'):
+      * **sort**(<_array_>sortCriteria, <_array_>searchCriteria, <_function_>callback) - _(void)_ - Performs a sorted search(). A seqno-based counterpart exists for this function. The callback has two parameters: the error (falsey if none), and an array containing the message UIDs matching the search criteria. Valid sortCriteria are (reverse sorting of individual criteria is done by prefixing the criteria with '-'):
 
         * ARRIVAL - Internal date and time of the message.  This differs from the ON criteria in search(), which uses just the internal date.