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.
npx agentmods add instructions/posit-dev/skills/claude-mdgit clone --depth 1 https://github.com/posit-dev/skillsWhat 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.
| Model | Per session | Once invoked |
|---|---|---|
| Fable 5 | $0.00856 | $0.00856 |
| Opus 5 | $0.00428 | $0.00428 |
| Sonnet 5 | $0.00171 | $0.00171 |
| Haiku 4.5 | $0.00086 | $0.00086 |
Grade A, and why
skills CLAUDE.md 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 3d 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.
How it starts
The opening of the file, as written. The whole thing — 88 lines — stays where its author put it; the contents beside it link to each section on GitHub.
CLAUDE.md
This file provides guidance to Claude Code (claude.ai/code) when working with code in this repository.
What This Repository Is
A collection of Claude Skills published by Posit PBC. Skills are structured markdown files that teach Claude specialized workflows (e.g., Shiny app development, R package testing, GitHub PR workflows). There is no application code to build, compile, or deploy — the primary artifacts are Markdown files consumed directly by Claude's skill system.
Utility Script
The only runnable utility is count-skill-tokens.py, which reports line and token counts for a skill:
# Requires uv
./count-skill-tokens.py shiny/shiny-bslib
# or
uv run count-skill-tokens.py r-lib/cli
Warns when SKILL.md exceeds 5,000 tokens / 500 lines, or when the skill description frontmatter exceeds 100 tokens.
Directory Structure
<category>/
README.md # Category-level notes (optional per skill)
<skill-name>/
SKILL.md # Required: skill definition with YAML frontmatter
references/ # Optional: supplementary docs loaded on demand
*.md
scripts/ # Optional: R or shell helpers
templates/ # Optional: document templates
Do not create a README.md inside individual skill directories — documentation about a skill's design goes in the category README.
SKILL.md Format
Every skill requires YAML frontmatter at minimum:
---
name: your-skill-name # kebab-case, matches directory name
description: > # Claude reads this to decide when to activate the skill
Clear description of what this skill does and when to trigger it.
Keep under 100 tokens.
---
The body is instructions written for Claude, not end users — imperative, step-by-step, covering edge cases.
Registering a New Skill
After creating the skill directory, add it to the appropriate plugin in .claude-plugin/marketplace.json:
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.
- 3d ago First seen · 88 lines · 856 tokens per session scan A b92fd0f7bd0f
skills CLAUDE.md is an instructions file published in the GitHub repository posit-dev/skills (488 stars, last pushed 5d ago), licensed MIT. It adds 856 tokens to every session, about $0.0043 per session on Opus 5. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-30.
Other instructions, from other repositories
vscode buildNext.instructions.md
Working notes and architecture documentation for the new esbuild-based build system in build/next. Use when making changes to the new build pipeline (transpile/bundle commands, NLS plugin, source-map handling, resource copying, or self-hosting watch tasks).
spec-kit AGENTS.md
AGENTS.md instructions for github/spec-kit, covering agents.md, about spec kit and specify, quickstart — add a new integration in 5 steps, integration architecture and integrationmanifest — file tracking.
codex AGENTS.md
AGENTS.md instructions for openai/codex, covering rust/codex-rs, the codex-core crate, code review rules, crate api surface and model visible context.
langchain AGENTS.md
AGENTS.md instructions for langchain-ai/langchain, covering global development guidelines for the langchain monorepo, corridor security analysis, project architecture and context, monorepo structure and development tools & commands.
vscode oss-third-party-notices.instructions.md
Instructions for microsoft/vscode, covering vs code oss third-party-notices pipeline, architecture, pipeline flow in ci, applying the notice (cutover) and fallback chain (never fail the build).
next.js AGENTS.md
Instructions for vercel/next.js, covering next.js development guide, codebase structure, monorepo overview, core package: packages/next and other important packages.