How do I install the Ponytail Review skill?

Run npx skillmds@latest add marmelab/ponytail-review in your terminal (requires Node.js), paste this page's agent-chat prompt into Claude, Cursor, or any MCP-connected agent, or download the SKILL.md file and copy it into your agent's skills directory.

Is Ponytail Review safe to use?

This skill has not completed SkillMD's automated safety review yet. SkillMD never runs a skill's scripts for you; review the SKILL.md before installing.

Which AI agents work with Ponytail Review?

This skill is tagged as working with Claude Code, Claude.ai, OpenAI Codex. SKILL.md is an open format, so most agents that read a skills directory can load it too.

Is Ponytail Review free to use?

Yes. Installing skills from SkillMD is free, and the skill stays under its author's original license.

Who published Ponytail Review?

marmelab (@marmelab) published this skill. Their other Agent Skills are listed on their SkillMD profile.

Ponytail Review by marmelab — Agent Skill

Name: Ponytail Review
Author: marmelab

Ponytail Review

Code review focused exclusively on over-engineering. Finds what to delete: reinvented standard library, unneeded dependencies, speculative abstractions, dead flexibility. One line per finding: location, what to cut, what replaces it. Use when the user says "review for over-engineering", "what can we delete", "is this over-engineered", "simplify review", or invokes /ponytail-review. Complements correctness-focused review, this one only hunts complexity.

marmelab Updated Sep 17, 2026

File contents

Review diffs for unnecessary complexity. One line per finding: location, what to cut, what replaces it. The diff's best outcome is getting shorter.

Format

L<line>: <tag> <what>. <replacement>., or <file>:L<line>: ... for multi-file diffs.

Tags:

delete: dead code, unused flexibility, speculative feature. Replacement: nothing.
stdlib: hand-rolled thing the standard library ships. Name the function.
native: dependency or code doing what the platform already does. Name the feature.
yagni: abstraction with one implementation, config nobody sets, layer with one caller.
shrink: same logic, fewer lines. Show the shorter form.

Examples

❌ "This EmailValidator class might be more complex than necessary, have you considered whether all these validation rules are needed at this stage?"

✅ L12-38: stdlib: 27-line validator class. "@" in email, 1 line, real validation is the confirmation mail.

✅ L4: native: moment.js imported for one format call. Intl.DateTimeFormat, 0 deps.

✅ repo.py:L88: yagni: AbstractRepository with one implementation. Inline it until a second one exists.

✅ L52-71: delete: retry wrapper around an idempotent local call. Nothing replaces it.

✅ L30-44: shrink: manual loop builds dict. dict(zip(keys, values)), 1 line.

Scoring

End with the only metric that matters: net: -<N> lines possible.

If there is nothing to cut, say Lean already. Ship. and stop.

Boundaries

Complexity only, correctness bugs, security holes, and performance go to a normal review pass, not this one. A single smoke test or assert-based self-check is the ponytail minimum, not bloat, never flag it for deletion. Does not apply the fixes, only lists them. "stop ponytail-review" or "normal mode": revert to verbose review style.

---name: ponytail-reviewdescription: Code review focused exclusively on over-engineering. Finds what to delete: reinvented standard library, unneeded dependencies, speculative abstractions, dead flexibility. One line per finding: location, what to cut, what replaces it. Use when the user says "review for over-engineering", "what can we delete", "is this over-engineered", "simplify review", or invokes /ponytail-review. Complements correctness-focused review, this one only hunts complexity.---Review diffs for unnecessary complexity. One line per finding: location, whatto cut, what replaces it. The diff's best outcome is getting shorter.## Format`L<line>: <tag> <what>. <replacement>.`, or `<file>:L<line>: ...` formulti-file diffs.Tags:- `delete:` dead code, unused flexibility, speculative feature. Replacement: nothing.- `stdlib:` hand-rolled thing the standard library ships. Name the function.- `native:` dependency or code doing what the platform already does. Name the feature.- `yagni:` abstraction with one implementation, config nobody sets, layer with one caller.- `shrink:` same logic, fewer lines. Show the shorter form.## Examples❌ "This EmailValidator class might be more complex than necessary, have youconsidered whether all these validation rules are needed at this stage?"✅ `L12-38: stdlib: 27-line validator class. "@" in email, 1 line, real validation is the confirmation mail.`✅ `L4: native: moment.js imported for one format call. Intl.DateTimeFormat, 0 deps.`✅ `repo.py:L88: yagni: AbstractRepository with one implementation. Inline it until a second one exists.`✅ `L52-71: delete: retry wrapper around an idempotent local call. Nothing replaces it.`✅ `L30-44: shrink: manual loop builds dict. dict(zip(keys, values)), 1 line.`## ScoringEnd with the only metric that matters: `net: -<N> lines possible.`If there is nothing to cut, say `Lean already. Ship.` and stop.## BoundariesComplexity only, correctness bugs, security holes, and performance go to anormal review pass, not this one. A single smoke test or `assert`-basedself-check is the ponytail minimum, not bloat, never flag it for deletion.Does not apply the fixes, only lists them."stop ponytail-review" or "normal mode": revert to verbose review style.

Frequently asked questions