ponytail/README.md

Ponytail

A skill that makes your AI agent think like the laziest senior dev in the room —
because the best code is the code you never wrote.

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The Problem

AI coding agents are overenthusiastic by default. Give them a simple task and they will:

• Write 200 lines where 5 would work
• Build custom implementations when the standard library already has it
• Add dependencies when a native feature exists
• Generate boilerplate nobody asked for
• Abstract everything, over-engineer everything

Ponytail fixes this.

What Ponytail Is

Ponytail is an AI agent skill. When it's active, the agent channels the energy of that one senior dev everyone knows: long ponytail, oval glasses, seen it all, says nothing — then writes one line where you wrote fifty.

Before writing any code, the agent walks this ladder and stops at the first rung that holds:

1. Does this need to be built at all?          → YAGNI
2. Does the standard library already do this?  → use it
3. Does a native platform feature cover this?  → use it
4. Does an existing package solve this?        → use it
5. Can this be done in one line?               → do it
6. Only then: write the minimum code that works

Intentional simplifications are marked with a ponytail: comment, so simple reads as deliberate — not naive.

Examples

Task	Without Ponytail	With Ponytail
Email validation	27-line validator class	"@" in email — or let the confirmation mail reject it
Date picker	flatpickr + wrapper component	<input type="date">
Sorting	hand-rolled quicksort	arr.sort((a, b) => a - b)
Caching	120-line TTL cache class	@lru_cache — or nothing until you measure
API endpoint	5 files of layers	5 lines

Full before/after in examples/.

Install

Claude Code — plugin (full integration)

/plugin marketplace add DietrichGebert/ponytail
/plugin install ponytail@ponytail

Auto-activation every session, /ponytail levels, /ponytail-review, /ponytail-help, [PONYTAIL] statusline badge. Restart Claude Code after install.

Claude Code — skill only

git clone https://github.com/DietrichGebert/ponytail.git
cp -r ponytail/skills/ponytail ~/.claude/skills/   # personal, all projects
# or: cp -r ponytail/skills/ponytail .claude/skills/   # this project only

Cursor — copy .cursor/rules/ponytail.mdc into your project.

Windsurf — copy .windsurf/rules/ponytail.md.

Cline — copy .clinerules/ponytail.md.

Aider — aider --read AGENTS.md with AGENTS.md in the repo root.

GitHub Copilot — copy .github/copilot-instructions.md.

Levels

Level	Trigger	What changes
lite	/ponytail lite	Builds what's asked, names the lazier alternative in one line.
full	/ponytail	The ladder enforced. Questions necessity, stdlib first, shortest diff. Default.
ultra	/ponytail ultra	YAGNI extremist. Deletion before addition. Challenges the requirement before building.

Deactivate: say "stop ponytail" / "normal mode", or /ponytail off.

Commands

Command	What it does
/ponytail [lite|full|ultra|off]	Switch level
/ponytail-review	Over-engineering review — L42: yagni: factory, one product. Inline.
/ponytail-help	Reference card

Configure

The plugin auto-activates at full every session. Change the default:

export PONYTAIL_DEFAULT_MODE=ultra   # env var, highest priority

or ~/.config/ponytail/config.json (Windows: %APPDATA%\ponytail\config.json):

{ "defaultMode": "off" }

off = no auto-activation, /ponytail still works on demand. Statusline badge ([PONYTAIL], [PONYTAIL:ULTRA]) offers to configure itself if no statusline is set.

Trigger Words

With Claude Code the skill activates on its own when you say any of:

ponytail · be lazy · lazy mode · simplest solution · minimal solution · yagni · do less · shortest path

— or when you complain about over-engineering. Other tools apply rules files unconditionally.

Token Savings

Ponytail saves tokens on two levels at once:

1. Shorter output — less code written, fewer output tokens.
2. Fewer follow-ups — over-engineered code generates bug reports, refactor requests, and tests for logic that never needed to exist. Ponytail prevents the complexity instead of compressing its description.

Measured (5 coding tasks, fresh agent per run, same model):

Config	Agent tokens	Time	Code written
No skill	161,955	479s	~293 lines
Caveman	138,410	136s	~117 lines
Ponytail	136,624	158s	~47 lines

The no-skill baseline produced a 190-line countdown "dashboard" where ponytail shipped 13 lines. Full data: benchmarks/.

Comparison to Caveman

	Caveman	Ponytail
Core idea	Answer short	Solve minimal
Target	Response verbosity	Code complexity
Token savings	Output shorter	Output shorter + fewer follow-ups
Character	Primitive caveman	Tired senior dev

Same category — a character skill with a measurable effect — different problem. They stack nicely.

License

MIT. Ponytail would have chosen the shortest license anyway.