Writing your own skill is actually a lot better for context efficiency.

Your skill will be tuned to your use case over time, so if there's something that you do a lot you can hide most of the back-and-forth behind the python script / cli tool.

You can even improve the skill by saying "I want to be more token efficient, please review our chat logs for usage of our skill and factor out common operations into new functions".

If anything context waste/rot comes from documentation of features that other people need but you don't. The skill should be a sharp knife, not a multi-tool.