ruff

ruff is a skill for Claude Code from moabualruz/fulcrum. It costs 65 tokens per session (215 once invoked), scanned A, a copy of bat, MIT.

A command-line tool that checks and formats Python code. Linting finds likely errors and style problems, while formatting rewrites code into a consistent layout.

In plain words
What is it for?
Use ruff check to lint, fix, sort imports, and apply rules, and use ruff format to format Python code in a style compatible with Black.
Why use it?
It combines two routine Python code-quality tasks and can also sort imports, apply fixes, and check for some security issues.

Skill for Claude Code

Written for Claude Code: shipped in a Claude Code plugin.

Part of the fulcrum plugin — 32 skills shipped together

Good fit Use ruff check to lint, fix, sort imports, and apply rules, and use ruff format to format Python code in a style compatible with Black.

Compare 6 skills from other repositories ↓
Install with agentmods
npx agentmods add skills/moabualruz/fulcrum/ruff
Install

Getting it into your agent

One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.

Any agent
npx skills add moabualruz/fulcrum --skill ruff
Clone the repo
git clone --depth 1 https://github.com/moabualruz/fulcrum

Made for: Claude Code.

Or install fulcrum, the plugin that ships this one along with the rest of its 32 skills.

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 ruff

README.md
[![agentmods](https://agentmods.dev/badge/skills/moabualruz/fulcrum/ruff.svg)](https://agentmods.dev/skills/moabualruz/fulcrum/ruff)
Your own site
<a href="https://agentmods.dev/skills/moabualruz/fulcrum/ruff"><img src="https://agentmods.dev/badge/skills/moabualruz/fulcrum/ruff.svg" alt="Measured on agentmods" height="20"></a>
Per session 65 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 215 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 84% 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 $0.00065 $0.00215
Opus 5 $0.00032 $0.00108
Sonnet 5 $0.00013 $0.00043
Haiku 4.5 $0.00006 $0.00021

Measured 7d ago against content hash 72ddb2623d12, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-07, from the pricing page.

Security

Grade A, and why

ruff 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 7d 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

84% identical to bat — 6 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.

plugins/fulcrum/skills/ruff/SKILL.md · 28 lines

What it actually says

ruff

When to use

See references/when-to-use.md. Load only when this section is needed.

Invocation

See references/invocation.md. Load only when this section is needed.

Patterns

See references/patterns.md. Load only when this section is needed.

Anti-patterns

See references/anti-patterns.md. Load only when this section is needed.

Cross-refs

See references/cross-refs.md. Load only when this section is needed.

Files

What ships with it

5 files beside SKILL.md in the same directory: the scripts, references and assets a skill reads on demand. Not counted in the per-session cost; read them before you install if any of them is executable.

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. 7d ago First seen · 28 lines · 65 tokens per session scan A 72ddb2623d12

Subscribe to this mod's changes

ruff is a skill published in the GitHub repository moabualruz/fulcrum (3 stars, last pushed 2mo ago), licensed MIT. It adds 65 tokens to every session and 215 once invoked, about $0.0003 per session on Opus 5. A static security scan graded it A with 0 findings. It is 84% identical to bat, differing in 6 lines, and is treated as a copy.