Thats exactly how I use skills as well and I got great results with it. I work in a proprietary codebase with a lot of niche or custom tooling, weird technical details and historical quirks. What skills do for me, is essentially skip the "learning" phase of an agent working in the codebase. With a fitting skill the agent does not need to read the tooling docs, look at existing repos and learn the coding style, but it can get to work immediately.

This is probably less relevant for code that exists a ton in the LLM training data already as an llm is probably competent to some degree in that anyway.

A big caveat here is though that now you need to treat your skills repo very carefully as mistakes in there can easily spread to all of the new code you write using a coding agent.