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Purity Check

Category: General  ·  Sub-category: general-misc  ·  Last updated:
type:review
Enforces functional-core purity rules: PURE-1 (no side effects in core/ modules — no I/O, no clock, no RNG, no logging), PURE-2 (no ambient/global state reads in core), PURE-3 (mock-required-to-test signal — if a function needs a mock to test, it isn't pure and belongs in shell). Loaded by the conductor for write and review operations when core-layer code is in scope. Layer detection follows the conductor's Section 14.
Security AStatic scan found no risk patternsHow grading works ›

From the source SKILL.md

The functional core / impure shell pattern is the single biggest lever for keeping AI-generated code testable and reasonable. Pure functions: - Need no DI container, no mocks, no fixtures — only inputs and outputs. - Are trivially testable: literal inputs, literal expected outputs. - Don't decay under refactors (no hidden coupling to globals). - Don't surprise readers (everything they read is in the signature).

What this skill does

Purity Check is a community-contributed Claude Code skill in the general-misc sub-category. It ships as a SKILL.md file that Claude Code auto-discovers under ~/.claude/skills/purity-check/ and loads when your prompt matches the skill's trigger.

Who uses this skill

The Purity Check Claude Code skill is built for Claude Code users and developers across all disciplines looking for general-purpose AI assistance. It's part of ClaudSkills (also referred to as Claude Skills or Claude Code Skills) — the open community-curated registry of 196,000+ SKILL.md files for Anthropic's Claude Code agent and the wider Claude ecosystem (Claude API, Claude Agent SDK).

How to install

Free

Manual install (2 steps)

mkdir -p ~/.claude/skills/purity-check
curl -L https://claudskills.com/skills/purity-check/SKILL.md \
  -o ~/.claude/skills/purity-check/SKILL.md

Or just download SKILL.md directly and drop it into ~/.claude/skills/purity-check/. Claude Code auto-discovers it on next session.

Skills live at ~/.claude/skills/purity-check/SKILL.md on macOS/Linux, or %USERPROFILE%\.claude\skills\purity-check\SKILL.md on Windows. See the full install guide for step-by-step instructions.

Telegram

📱 Install from your phone or desktop Telegram

Open @claudskills_bot on Telegram, tap Open Desktop App, and the desktop app installs this skill for you. Or share the bot link with a colleague — they get the same one-tap install. Learn more →

Pro

One-click install via the desktop app

The ClaudSkills desktop app installs any skill directly into ~/.claude/skills/ with one click — no terminal required. Pro starts at $9/mo or $149 lifetime.

Pro

For the full experience including quality scoring and one-click install features for each skill — upgrade to Pro.

See pricing → Download desktop app

Frequently asked questions

How do I install the Purity Check Claude Code skill?
Install via the ClaudSkills desktop app (one click) or copy SKILL.md from the source repository to ~/.claude/skills/purity-check/SKILL.md and restart Claude Code. Both flows are detailed at claudskills.com/install/.
What does the Purity Check skill do?
Enforces functional-core purity rules: PURE-1 (no side effects in core/ modules — no I/O, no clock, no RNG, no logging), PURE-2 (no ambient/global state reads in core), PURE-3 (mock-required-to-test signal — if a function needs a mock to test, it isn't pure and belongs in shell). Loaded by the conductor for write and review operations when core-layer code is in scope. Layer detection follows the conductor's Section 14.
Is this skill free to install?
Yes. ClaudSkills is an open registry — every skill keeps its source repository's license, and manual install via copy is free. ClaudSkills Pro ($9/mo, $79/yr, or $149 one-time) adds one-click install via the desktop app and a multi-signal Quality Score.
When should I use the Purity Check skill?
Use Purity Check when your Claude Code task falls under the General category — specifically in the general misc area. Claude Code auto-discovers installed skills and invokes the right one based on the task description, so you can also ask Claude directly (e.g. "use Purity Check" or describe the task and let Claude pick). Browse related skills at /category/general/.
What is a Claude Code skill and how does the Purity Check skill fit in?
A Claude Code skill is a SKILL.md file that lives under ~/.claude/skills/<name>/ and tells the Claude Code CLI agent how to perform a specific task (instructions, prompts, allowed tools). Skills are auto-discovered at session start. Purity Check is one of 67,000+ skills indexed in the open ClaudSkills catalog, classified under the General category. Learn more at /learn/what-is-a-claude-skill/.

Attribution & license

Cite this skill

If you reference this skill in a blog post, paper, or documentation, you can cite it as:

APA
mikecubed. (2026). Purity Check [Claude Code skill]. ClaudSkills. https://claudskills.com/skills/purity-check/
BibTeX
@misc{purity-check-2026,
  author    = {mikecubed},
  title     = {Purity Check [Claude Code skill]},
  year      = {2026},
  publisher = {ClaudSkills},
  url       = {https://claudskills.com/skills/purity-check/}
}

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Security scan

Grade A · scanned 2026-09-28 — free static scan against the OWASP Agentic Skills Top 10.

The scan flagged 1 of 10 categories (filesystem), including lower-severity patterns. Patterns shown inside code fences are weighted as examples rather than instructions — read the grading methodology for what this does and does not guarantee.

Show this grade on your repo (click to copy):

[![Security: A](https://img.shields.io/badge/Security-A-2e7d32)](https://claudskills.com/skills/purity-check/#security)

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