# Principle Build The Lever

> Apply to any non-trivial work, not just bulk work: edits, migrations, analyses, checks.

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.

- Page: https://ss33.ai/skills/cursor/principle-build-the-lever-34531241557
- Publisher: cursor
- Category: [AI & Agents](https://ss33.ai/skills/category/ai-and-agents-y6jz7i) › [Skill & prompt authoring](https://ss33.ai/skills/category/ai-and-agents-y6jz7i/skill-and-prompt-authoring-p179rh)
- License: MIT
- Source: https://github.com/cursor/plugins/blob/d457567332aa6989e753ea289f30ea2bfbc80bc0/harness/pstack/claude-code/skills/principle-build-the-lever/SKILL.md

## Skill

SKILL.md: https://ss33.ai/api/v1/ss33/download/cursor/principle-build-the-lever-34531241557

# 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.
- 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](../principle-laziness-protocol/SKILL.md), build the smallest script that does or proves the job, never a framework.

Distinct from [Encode Lessons in Structure](../principle-encode-lessons-in-structure/SKILL.md), 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-prove-it-works/SKILL.md).