Yes, C# has a reputation for being good for tools-dev within the games industry.
If I may ask: Isn't C# particulary good for making tools? I have read this several times in different websites over the last couple years or so. Is this a myth or a reality?
If you wanted to make Windows GUIs, the Microsoft solution used to be to use C++ with MFC, but C#.NET has since blown C++/MFC away for productivity. Visual studio comes with a good WYSIWYG GUI editor, and C#.NET has a huge standard library of tools, and it's popular enough that searching for "how do I x in C#" almost always brings up a StackExchange thread telling you how.
N.B. it's not the only choice for tools-dev, e.g. you can still use C++ and MFC, or C++ and Qt, or Python and WxWidgets (the list of options is endless...), but I'd personally recommend C# for this task over C++.
On my personal project, and at my last two jobs, we've used C# to make the game's tool-chain, and C++ to make the game-engine runtimes.