Apply to any non-trivial work, not just bulk work: edits, migrations, analyses, checks. Build the tool that does it or proves it (codemod, script, generator, or a skill your subagents follow) instead of working by hand. The tool is the artifact a reviewer can rerun.
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Use principle-build-the-lever to create a small, safe-to-rerun tool in [repository] that performs or verifies [non-trivial work] against [acceptance criteria].
Required inputs
[repository]
[non-trivial work]
[acceptance criteria]
User-approved starter prompt based on a pinned source version; check current skill requirements before running. Task evidence ↗
SKILL.md
name: principle-build-the-leverdescription: "Apply to any non-trivial work, not just bulk work: edits, migrations, analyses, checks. Build the tool that does it or proves it (codemod, script, generator, or a skill your subagents follow) instead of working by hand. The tool is the artifact a reviewer can rerun."user-invocable: false
Build the Lever
When the work isn't trivial, build the tool that does it instead of doing it by hand.
A codemod, generator, or script does the work the same way every time and reruns for free. The tool is one artifact a reviewer can read and rerun to check the work. Hand-done changes can only be re-verified by redoing them. A deterministic script turns "trust me" into "run this".
Default to building the lever. Skip it only when the task is trivial, a couple of obvious edits you can see at a glance.
Do the first unit by hand to learn the recipe, then build the tool. Prove it by rerunning it on that unit and diffing against your hand-done version. Make the lever safe to rerun.
For a comparison tool, seed one known-bad change for each output it claims to compare, and confirm the tool reports each mismatch. For example, change a total, then separately swap item assignments while keeping the totals. If required input is missing, the tool must refuse or report the result as inconclusive, never as a match. Keep these controls with the experiment and rerun them before you trust its results.
Codemod or script for edits, generator for repetitive files, a dump-to-sqlite query for analysis, a rerunnable check for verification.
A deterministic lever beats fan-out. If the tool can process every unit in one pass, run it yourself. Don't fan out delegates to hand-apply what a script can do.
When you fan work out to subagents, write the lever as a skill they all read: the recipe, the verification contract, and the do-not-touch fences in one artifact. Keep it outside the delegates' write scope so they can't quietly edit the contract.
Applying this principle produces a file. If you cited it and there is no codemod, script, generator, or delegate skill in the diff, you didn't apply it.
Commit the lever when the work outlives the session.
The bar is triviality, not repetition. A one-off still earns a lever when the lever is what makes the work checkable. Per the Laziness Protocol, build the smallest script that does or proves the job, never a framework.
Distinct from Encode Lessons in Structure, which makes a recurring instruction a durable guardrail. This is throughput and reviewability on the work in front of you. For scripting the verification itself, see Prove It Works.
principle-build-the-lever by michael-denyer · The Skill Leaderboard