pseolint: Skill for Claude Code

.claude/skills/ponytail/SKILL.md

ponytail is a skill for Claude Code from ouranos-labs/pseolint. It costs 138 tokens per session (1,270 once invoked), scanned A, a copy of ponytail, MIT.

A coding skill that pushes toward the smallest solution that meets the request. It applies YAGNI—“You Aren’t Gonna Need It”—by questioning unnecessary work before adding code.

In plain words
What is it for?
Use it when building or changing software to choose among no change, the standard library, native features, existing dependencies, or the minimum custom code.
Why use it?
It reduces over-engineering, extra dependencies, abstractions, and maintenance work by preferring existing language or platform features.

Skill for Claude Code

Written for Claude Code: installed under .claude/.

This is ouranos-labs/pseolint's own configuration. It tells Claude Code how to work on pseolint itself, so it is not a mod to install elsewhere. Copy it as a starting point and replace the rules that are about this project. Everything pseolint configures →

Reuse

Borrowing it

Nothing to install: this file belongs to ouranos-labs/pseolint. Take a copy, put it at the same path in your own repository, and replace the rules that are about this project with yours.

Copy the file
curl -O https://raw.githubusercontent.com/ouranos-labs/pseolint/main/.claude/skills/ponytail/SKILL.md
Clone the repo
git clone --depth 1 https://github.com/ouranos-labs/pseolint

Made for: Claude Code.

Wrote this? Show the measurements

A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.

agentmods badge for ponytail

README.md
[![agentmods](https://agentmods.dev/badge/skills/ouranos-labs/pseolint/ponytail/github.svg)](https://agentmods.dev/skills/ouranos-labs/pseolint/ponytail)
Your own site
<a href="https://agentmods.dev/skills/ouranos-labs/pseolint/ponytail"><img src="https://agentmods.dev/badge/skills/ouranos-labs/pseolint/ponytail/github.svg" alt="Measured on agentmods" height="20"></a>

Or the 80×15 button, for a site that already has a row of RSS and ATOM ones. Only the verdict fits; the numbers stay here.

agentmods 80×15 button for ponytail

Your own site · 80×15
<a href="https://agentmods.dev/skills/ouranos-labs/pseolint/ponytail"><img src="https://agentmods.dev/badge/skills/ouranos-labs/pseolint/ponytail.svg" alt="Reviewed on agentmods" width="80" height="20"></a>
Per session 138 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 1,270 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. A grade says what 26 rules found in the file — not that it is safe.
Origin 95% copy Near-identical to another mod in the catalogue.
Token cost

What it costs to keep this loaded

Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.

ModelPer sessionOnce invoked
Fable 5.1 $0.00138 $0.01270
Opus 5 $0.00069 $0.00635
Sonnet 5 $0.00028 $0.00254
Haiku 4.5 $0.00014 $0.00127

Measured 10d ago against content hash 1b9eaae4b639, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-10, from the pricing page.

Security

Grade A, and why

ponytail scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 10d ago.

A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.

Nothing flagged

None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.

Origin

This is a copy

95% identical to ponytail — 10 lines differ, which has more behind it and is treated as the original. This page carries a canonical link to it rather than competing with it.

.claude/skills/ponytail/SKILL.md · 101 lines

How it starts

The opening of the file, as written. The whole thing — 101 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Ponytail

You are a lazy senior developer. Lazy means efficient, not careless. You have seen every over-engineered codebase and been paged at 3am for one. The best code is the code never written.

Persistence

ACTIVE EVERY RESPONSE. No drift back to over-building. Still active if unsure. Off only: "stop ponytail" / "normal mode". Default: full. Switch: /ponytail lite|full|ultra.

The ladder

Stop at the first rung that holds:

  1. Does this need to exist at all? Speculative need = skip it, say so in one line. (YAGNI)
  2. Stdlib does it? Use it.
  3. Native platform feature covers it? <input type="date"> over a picker lib, CSS over JS, DB constraint over app code.
  4. Already-installed dependency solves it? Use it. Never add a new one for what a few lines can do.
  5. Can it be one line? One line.
  6. Only then: the minimum code that works.

The ladder is a reflex, not a research project. Two rungs work → take the higher one and move on. The first lazy solution that works is the right one.

Rules

  • No unrequested abstractions: no interface with one implementation, no factory for one product, no config for a value that never changes.
  • No boilerplate, no scaffolding "for later", later can scaffold for itself.
  • Deletion over addition. Boring over clever, clever is what someone decodes at 3am.
  • Fewest files possible. Shortest working diff wins.
  • Complex request? Ship the lazy version and question it in the same response, "Did X; Y covers it. Need full X? Say so." Never stall on an answer you can default.
  • Two stdlib options, same size? Take the one that's correct on edge cases. Lazy means writing less code, not picking the flimsier algorithm.
  • Mark deliberate simplifications with a ponytail: comment (// ponytail: this exists), simple reads as intent, not ignorance. Shortcut with a known ceiling (global lock, O(n²) scan, naive heuristic)? The comment names the ceiling and the upgrade path: # ponytail: global lock, per-account locks if throughput matters.

Read the full file on GitHub · 101 lines

Changes

What this file has done since we first saw it

Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.

  1. 10d ago First seen · 101 lines · 138 tokens per session scan A 1b9eaae4b639

Subscribe to this mod's changes

ponytail is a skill published in the GitHub repository ouranos-labs/pseolint (6 stars, last pushed 3d ago), licensed MIT. It adds 138 tokens to every session and 1,270 once invoked, about $0.0007 per session on Opus 5. A static security scan graded it A with 0 findings. It is 95% identical to ponytail, differing in 10 lines, and is treated as a copy.

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