add-and-validate-guardian-developer-semgrep-rule

add-and-validate-guardian-developer-semgrep-rule is a skill for Claude Code from semgrep/guardian. It costs 81 tokens per session (2,142 once invoked), scanned A, original, no licence file.

A workflow for writing and installing a custom Semgrep rule in Guardian. Semgrep is a code-scanning tool that finds patterns in source files, and the workflow checks the new rule by creating code that should trigger it.

In plain words
What is it for?
It helps create a rule, add it for one user or a repository, and verify that Guardian reports a matching file.
Why use it?
It helps enforce a project convention or catch a code pattern that Guardian does not currently detect, while checking that the rule really works.

Skill for Claude Code

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

Part of the semgrep plugin — 3 skills, 5 hooks, 1 MCP server shipped together

Good fit It helps create a rule, add it for one user or a repository, and verify that Guardian reports a matching file.

Compare 6 skills from other repositories ↓
Install with agentmods
npx agentmods add skills/semgrep/guardian/add-and-validate-guardian-developer-semgrep-rule
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 semgrep/guardian --skill add-and-validate-guardian-developer-semgrep-rule
Clone the repo
git clone --depth 1 https://github.com/semgrep/guardian

Made for: Claude Code.

Or install semgrep, the plugin that ships this one along with the rest of its 3 skills, 5 hooks, 1 MCP server.

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 add-and-validate-guardian-developer-semgrep-rule

README.md
[![agentmods](https://agentmods.dev/badge/skills/semgrep/guardian/add-and-validate-guardian-developer-semgrep-rule/github.svg)](https://agentmods.dev/skills/semgrep/guardian/add-and-validate-guardian-developer-semgrep-rule)
Your own site
<a href="https://agentmods.dev/skills/semgrep/guardian/add-and-validate-guardian-developer-semgrep-rule"><img src="https://agentmods.dev/badge/skills/semgrep/guardian/add-and-validate-guardian-developer-semgrep-rule/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 add-and-validate-guardian-developer-semgrep-rule

Your own site · 80×15
<a href="https://agentmods.dev/skills/semgrep/guardian/add-and-validate-guardian-developer-semgrep-rule"><img src="https://agentmods.dev/badge/skills/semgrep/guardian/add-and-validate-guardian-developer-semgrep-rule.svg" alt="Reviewed on agentmods" width="80" height="20"></a>
Per session 81 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 2,142 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 1 finding. A grade says what 26 rules found in the file — not that it is safe.
Origin unknown No closer match found 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 $0.00081 $0.02142
Opus 5.5 $0.00032 $0.00857
Sonnet 5.5 $0.00016 $0.00428
Haiku 4.5 $0.00008 $0.00214

Measured 17d ago against content hash cde31a31c56f, method: parsed. Prices are Anthropic first-party input rates as of 2026-10-07, from the pricing page.

Security

Grade A, and why

add-and-validate-guardian-developer-semgrep-rule scanned grade A with 1 finding 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 17d 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.

Makes network callslowCapability

Not a fault in itself. Listed so you know the mod talks to something, and to what.

message: use the retrying client in lib/http.py, not requests.get directly.
plugin/skills/add-and-validate-guardian-developer-semgrep-rule/SKILL.md · 178 lines

The source is not reproduced here

No licence file

A repository with no LICENSE is all rights reserved by default, so the body is not copied here. The metadata, the measurements and the link are.

Read it on GitHub

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. 17d ago Changed cde31a31c56f
  2. 23d ago First seen · 178 lines · 81 tokens per session scan A 2a97b60aaa7d

Subscribe to this mod's changes

add-and-validate-guardian-developer-semgrep-rule is a skill published in the GitHub repository semgrep/guardian (17 stars, last pushed 6d ago), with no licence file. It adds 81 tokens to every session and 2,142 once invoked, about $0.0003 per session on Opus 5.5. A static security scan graded it A with 1 finding (makes network calls). No closer match exists in the catalogue, so it is treated as the original; first seen 2026-09-25.

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