Semgrep Custom Rule Builder 3

Q: What is a Claude Code skill and how does the Semgrep Custom Rule Builder 3 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. Semgrep Custom Rule Builder 3 is one of 67,000+ skills indexed in the open ClaudSkills catalog, classified under the Security category. Learn more at https://claudskills.com/learn/what-is-skill-md/.

Category: Security · Sub-category: appsec-tools · Last updated: 2026-05-21

lang:javascript

Creates custom Semgrep SAST rules using the semgrep CLI and rule schema YAML format. Supports pattern-either, metavariable-regex, and taint-mode tracking for detecting framework-specific vulnerabilities in Python, Go, and JavaScript.

About this skill (catalog notes)

Semgrep Custom Rule Builder 3 includes a dedicated installation section.

Source: agentskillexchange.com/skills/semgrep-custom-rule-builder-3
Indexed lastmod: 2026-05-21
Catalog position: Security · appsec-tools
Indexed related skills: 10

How Semgrep Custom Rule Builder 3 fits the catalog

Semgrep Custom Rule Builder 3 sits in the Security category under the appsec-tools sub-topic in the ClaudSkills catalog. There are 10 related skills indexed alongside it; comparing a few before installing usually reveals which fits your workflow best.

These notes are auto-generated from features detected in the SKILL.md file and from this catalog's structure — they aren't part of the source repository.

From the source SKILL.md

What this skill does

Semgrep Custom Rule Builder 3 is a community-contributed Claude Code skill in the appsec-tools sub-category. It ships as a SKILL.md file that Claude Code auto-discovers under ~/.claude/skills/semgrep-custom-rule-builder-3/ and loads when your prompt matches the skill's trigger.

Who uses this skill

The Semgrep Custom Rule Builder 3 Claude Code skill is built for security engineers, penetration testers, DevSecOps practitioners, and development teams hardening codebases and infrastructure. It's part of ClaudSkills (also referred to as Claude Skills or Claude Code Skills) — the open community-curated registry of 116,000+ 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/semgrep-custom-rule-builder-3
curl -L https://claudskills.com/skills/semgrep-custom-rule-builder-3/SKILL.md \
  -o ~/.claude/skills/semgrep-custom-rule-builder-3/SKILL.md

Or just download SKILL.md directly and drop it into ~/.claude/skills/semgrep-custom-rule-builder-3/. Claude Code auto-discovers it on next session.

Skills live at ~/.claude/skills/semgrep-custom-rule-builder-3/SKILL.md on macOS/Linux, or %USERPROFILE%\.claude\skills\semgrep-custom-rule-builder-3\SKILL.md on Windows. See the full install guide for step-by-step instructions.

📱 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 Semgrep Custom Rule Builder 3 Claude Code skill?

Install via the ClaudSkills desktop app (one click) or copy SKILL.md from the source repository to ~/.claude/skills/semgrep-custom-rule-builder-3/SKILL.md and restart Claude Code. Both flows are detailed at claudskills.com/install/.

What does the Semgrep Custom Rule Builder 3 skill do?

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 Semgrep Custom Rule Builder 3 skill?

Use Semgrep Custom Rule Builder 3 when your Claude Code task falls under the Security category — specifically in the appsec tools 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 Semgrep Custom Rule Builder 3" or describe the task and let Claude pick). Browse related skills at /category/security/.

What is a Claude Code skill and how does the Semgrep Custom Rule Builder 3 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. Semgrep Custom Rule Builder 3 is one of 67,000+ skills indexed in the open ClaudSkills catalog, classified under the Security category. Learn more at /learn/what-is-a-claude-skill/.

Attribution & license

Source: https://github.com/semgrep/semgrep
Website: https://agentskillexchange.com/skills/semgrep-custom-rule-builder-3

Cite this skill

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

APA

ClaudSkills. (2026). Semgrep Custom Rule Builder 3 [Claude Code skill]. ClaudSkills. https://claudskills.com/skills/semgrep-custom-rule-builder-3/

BibTeX

@misc{semgrep-custom-rule-builder-3-2026,
  author    = {ClaudSkills},
  title     = {Semgrep Custom Rule Builder 3 [Claude Code skill]},
  year      = {2026},
  publisher = {ClaudSkills},
  url       = {https://claudskills.com/skills/semgrep-custom-rule-builder-3/}
}

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