C# Web API Help Page - Additional Information for the Body Parameters shows "None."

Question

I am using the Microsoft ASP.Net Web API 2.2 Help Page version 5.2.3 and the additional information for the Body Parameters is showing "None". I have not been able to make it show any useful information. The other information is populated correctly.

Sample Class:

/// <summary>
/// Class for doing something.
/// </summary>
public class MyClass
{
    /// <summary>
    /// This text here shows fine as the Description.
    /// </summary>
    [Required(ErrorMessage = "This is needed!")]
    public int MyInt;
}

As far as I can tell, the additional information should be populated either as "Required" or as the text in the error message. I have already tried this answer: https://stackoverflow.com/a/35920075/5910024 to no avail.