Set the service type to search in AeServiceDescription:
AeServiceDescription.serviceType = 'search';
There should be one output parameter, Search Results, that returns the data.
To return a valuelist, the invoke() method should return name/value pairs representing the name/id of the objects returned.

List<Account> accountList = 
    [SELECT Name, id FROM Account WHERE OwnerId =:userRef LIMIT 20];
      for (Account account: accountList)
      {
         // For a search service, return name/id as parameters
         response.addParameter(account.Name, account.Id);
      }