ponytail-review
dietrichgebert/ponytail
Code review focused exclusively on over-engineering—finds what to delete.
What is ponytail-review?
Ponytail-review hunts for unnecessary complexity in code: reinvented standard library functions, unneeded dependencies, speculative abstractions, and dead flexibility. Use it when you want a simplification-focused review that complements correctness checks, outputting one-line findings with concrete replacements.
- Identifies dead code, unused flexibility, and speculative features marked for deletion
- Finds hand-rolled implementations that duplicate standard library functions
- Detects dependencies or code duplicating platform-native features
- Spots single-implementation abstractions and unnecessary layers (YAGNI)
- Suggests equivalent logic in fewer lines (shrink refactors)
- Outputs findings as `location: tag what. replacement.` format with net line savings
How to install ponytail-review
npx skills add https://github.com/dietrichgebert/ponytail --skill ponytail-reviewHow to use ponytail-review
- 1.Install the skill using the provided npm command
- 2.Invoke the review by saying 'review for over-engineering', 'what can we delete', 'is this over-engineered', 'simplify review', or use /ponytail-review
- 3.Read the one-line findings in `location: tag what. replacement.` format
- 4.Apply the suggested deletions or simplifications to reduce lines of code
- 5.Use 'stop ponytail-review' or 'normal mode' to return to standard verbose review
Use cases
- Review a pull request for over-engineering before merging
- Simplify a legacy codebase by identifying unnecessary abstractions
- Audit dependencies to find ones doing what the platform already provides
- Reduce boilerplate by finding manual loops or wrappers that can be inlined
- Validate that new code doesn't add speculative features or premature abstraction
- Backend and frontend developers seeking simplification-focused code review
- Teams wanting to reduce technical debt and unnecessary complexity
- Code reviewers focusing on maintainability and deletion over feature addition
- Developers refactoring or auditing existing codebases
ponytail-review FAQ
Correctness bugs, security holes, and performance issues. Route those to a normal review pass. A single smoke test or assert-based self-check is acceptable and won't be flagged for deletion.
It shows the total number of lines that could be deleted across all findings, e.g., 'net: -47 lines possible.' If the code is already lean, it says 'Lean already. Ship.'
No, it only lists findings and suggests replacements. You apply the fixes manually.
delete (dead code), stdlib (standard library duplication), native (platform feature duplication), yagni (single-implementation abstraction), and shrink (same logic, fewer lines).
Yes, it complements correctness-focused reviews. Use ponytail-review for complexity and simplification, then run standard review for bugs and security.
Full instructions (SKILL.md)
Source of truth, from dietrichgebert/ponytail.
name: ponytail-review description: > 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, 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
Scope: over-engineering and complexity only. Correctness bugs, security holes,
and performance are explicitly out of scope. Route them 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.
Related skills
More from dietrichgebert/ponytail and the wider catalog.
ponytail
Forces the laziest solution that actually works—question whether tasks need to exist, reach for stdlib first, ship minimal code.
ponytail-audit
Whole-repo audit for over-engineering: ranked list of what to delete, simplify, or replace.
ponytail-help
Quick-reference card for ponytail modes, skills, and commands.
ponytail-debt
Harvest ponytail: comments into a debt ledger to track deliberate shortcuts before they rot.
ponytail-gain
Display ponytail's measured benchmark impact as a compact ASCII scoreboard.