Off-the-shelf tools solve the problems every firm has. They do not solve the one your team hits every Tuesday because of how your projects are set up, what your client demands, or which legacy system you have to feed.
We build those tools properly: the add-in itself, a signed installer your IT department will accept, version management so an update does not break a live project, and documentation written for the person using it rather than for the developer who wrote it.
A tool nobody uses is a tool that failed. So the last step is always training the people who will open it every day, and staying available after release — because the first real bug report usually arrives in week two, not week one.