WebApi Help Page Description

According to this article you can use XML documentation comments to create the documentation. To enable this feature, open the file Areas/HelpPage/App_Start/HelpPageConfig.cs and uncomment the following line:

config.SetDocumentationProvider(new XmlDocumentationProvider(
    HttpContext.Current.Server.MapPath("~/App_Data/XmlDocument.xml")));

Now enable XML documentation. In Solution Explorer, right-click the project and select Properties. Select the Build page.

Under Output, check XML documentation file. In the edit box, type “App_Data/XmlDocument.xml”.

Add some documentation comments to the controller methods. For example:

/// <summary>
/// Gets some very important data from the server.
/// </summary>
public IEnumerable<string> Get()
{
    return new string[] { "value1", "value2" };
}

/// <summary>
/// Looks up some data by ID.
/// </summary>
/// <param name="id">The ID of the data.</param>
public string Get(int id)
{
    return "value";
}