Use the DataContract and DataMember attributes. They will work for both JSON and XML. The JSON properties might not work for all SerivceStack versions but I've confrimed it works with v4.
[System.Runtime.Serialization.DataContract]
public class Team : IReturn<Team>
{
[System.Runtime.Serialization.DataMember(Order = 3)]
public int Id { get; set; }
[System.Runtime.Serialization.DataMember(Order = 2)]
public string Name { get; set; }
[System.Runtime.Serialization.DataMember(Order = 1)]
public DateTime CreatedDate { get; set; }
}