We don't usually recommend building custom tools, when an existing solution is already available. In-house solutions tend to be tricky to maintain, and will need rework and support over time. You need a truly detailed reason for this to be a viable idea in many cases.
But sometimes custom tools are needed, given constraints or bespoke business model needs. We've helped clients build their own tools over the years, to help with specific requirements.
Tools shouldn't be created however for major changes on platforms, just because it presents a new problem. In the case of changing marketplace requirements for example, usually it's possible to take advantage of an existing provider, and let them stay on top of the changes.
We'd be hypocrites to suggest making tools is always a bad idea! But we are believers that you should make them for the right reasons. We can help figure that out. And if the tool still sounds like a good idea, let's get creative together.