public bool ErrorsReported { get; set; }For Revit links specifically, Revit will check this value to see if it should report errors about a given link in the Unresolved References dialog. An IExternalResourceUIServer can set this value to true to avoid redundant messages.
Note that it is possible for Revit to encounter errors internally even if the server successfully provides a reference. In general, this value should only be set to true if the server has reported an error condition.