Agent Skills: better-mousetraps

Evaluate build-vs-import decisions before writing new functionality. Use when (1) about to implement non-trivial functionality that likely exists as a library, (2) the user's request could be solved by an existing tool or package, (3) you catch yourself writing utility code (parsing, validation, HTTP, crypto, dates, etc.) that smells like a solved problem, or (4) planning a feature and need to weigh develop-in-house vs. adopt a dependency.