Its description says the skill should be used when a user runs /ub-mode or asks for the reduced principles. The prescribed sequence is: make the change work, make it right, then follow practice.
The file requires a failing test before a code change, the smallest change that passes it, and fixes to root causes rather than guards that only hide a crash. It asks agents to test observable behavior, sequence work into verifiable units, keep a log of actions and reasons, protect the main context window, clean up worktrees, and commit and push in small ordered commits.
For refactoring, the skill refers to crapper, dryer, and mutator tools for complexity, duplication, and mutation-related checks. It does not include those tools, state a version or release date, specify supported agent runtimes, or provide evidence that following the rules improves code quality or is used in production.