Recently I developed Automation Server for reports in Word and was surprised with
failure trying to get Help String for TypeLibrary

Recently I developed Automation Server for reports in Word and was surprised with failure trying to get Help String for TypeLibrary by following code

Var
  k, InfoCount : Integer;
  TypeLib : ITypeLib;
  TypeLibGUID : TGUID;
  ErrorStr: String;
  HRes : HResult;
  pbstrDocString, pbstrName : WideString;
begin
  Memo1.Lines.Clear;
  // InputGUIDString is given input string value
  TypeLibGUID := StringToGUID(InputGUIDString);
  // loads Type Library from registry
  HRes := LoadRegTypeLib(TypeLibGUID, 1, 0, 0, TypeLib);
  if Failed(HRes) then
    Exit;

  // believing in mind, that so it is in practice!
  InfoCount := TypeLib.GetTypeInfoCount;   for k:=0 to kInfoCount-1 do
    begin
      HRes := TypeLib.GetDocumentation(k, @pbstrName, @pbstrDocString, nil, nil);
      if Failed(HRes) then
        Continue;
      Memo1.Lines.Add(pbstrName + ': ' + pbstrDocString);
    end;

Here was no errors!
But the thing is that help string for Type Library resides beyond the range [0..kInfoCount-1] so
TypeLib.GetTypeInfoCount reports about ITypeInfo count, excluding ITypeInfo for himself.
Did you know about it?
To get Help String for self Type Library one must implement

  TypeLib.GetDocumentation(-1, @pbstrName, @pbstrDocString, nil, nil);

Isn't it unexpectedly for Delphi programmers? I didn't found anything about it in Delphi help!