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 skills add vigolium/piolium --skill semgrep-rule-variant-creatorgit clone --depth 1 https://github.com/vigolium/pioliumWrote 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.
[](https://agentmods.dev/skills/vigolium/piolium/semgrep-rule-variant-creator)<a href="https://agentmods.dev/skills/vigolium/piolium/semgrep-rule-variant-creator"><img src="https://agentmods.dev/badge/skills/vigolium/piolium/semgrep-rule-variant-creator/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.
<a href="https://agentmods.dev/skills/vigolium/piolium/semgrep-rule-variant-creator"><img src="https://agentmods.dev/badge/skills/vigolium/piolium/semgrep-rule-variant-creator.svg" alt="Reviewed on agentmods" width="80" height="20"></a>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.
| Model | Per session | Once invoked |
|---|---|---|
| Fable 5.1 | $0.00050 | $0.01813 |
| Opus 5 | $0.00025 | $0.00907 |
| Sonnet 5 | $0.00010 | $0.00363 |
| Haiku 4.5 | $0.00005 | $0.00181 |
Grade A, and why
semgrep-rule-variant-creator 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 11d 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.
This is a copy
94% identical to semgrep-rule-variant-creator — 23 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.
How it starts
The opening of the file, as written. The whole thing — 206 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Semgrep Rule Variant Creator
Port existing Semgrep rules to new target languages with proper applicability analysis and test-driven validation.
When to Use
Ideal scenarios:
- Porting an existing Semgrep rule to one or more target languages
- Creating language-specific variants of a universal vulnerability pattern
- Expanding rule coverage across a polyglot codebase
- Translating rules between languages with equivalent constructs
When NOT to Use
Do NOT use this skill for:
- Creating a new Semgrep rule from scratch (use
semgrep-rule-creatorinstead) - Running existing rules against code
- Languages where the vulnerability pattern fundamentally doesn't apply
- Minor syntax variations within the same language
Input Specification
This skill requires:
- Existing Semgrep rule - YAML file path or YAML rule content
- Target languages - One or more languages to port to (e.g., "Golang and Java")
Output Specification
For each applicable target language, produces:
<original-rule-id>-<language>/
├── <original-rule-id>-<language>.yaml # Ported Semgrep rule
└── <original-rule-id>-<language>.<ext> # Test file with annotations
Example output for porting sql-injection to Go and Java:
sql-injection-golang/
├── sql-injection-golang.yaml
└── sql-injection-golang.go
sql-injection-java/
├── sql-injection-java.yaml
└── sql-injection-java.java
Rationalizations to Reject
When porting Semgrep rules, reject these common shortcuts:
| Rationalization | Why It Fails | Correct Approach |
|---|---|---|
| "Pattern structure is identical" | Different ASTs across languages | Always dump AST for target language |
| "Same vulnerability, same detection" | Data flow differs between languages | Analyze target language idioms |
| "Rule doesn't need tests since original worked" | Language edge cases differ | Write NEW test cases for target |
| "Skip applicability - it obviously applies" | Some patterns are language-specific | Complete applicability analysis first |
| "I'll create all variants then test" | Errors compound, hard to debug | Complete full cycle per language |
| "Library equivalent is close enough" | Surface similarity hides differences | Verify API semantics match |
| "Just translate the syntax 1:1" | Languages have different idioms | Research target language patterns |
What ships with it
3 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.
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.
- 11d ago First seen · 206 lines · 50 tokens per session scan A 66f2ad2ca1f6
semgrep-rule-variant-creator is a skill published in the GitHub repository vigolium/piolium (133 stars, last pushed 1mo ago), licensed MIT. It adds 50 tokens to every session and 1,813 once invoked, about $0.0003 per session on Opus 5. A static security scan graded it A with 0 findings. It is 94% identical to semgrep-rule-variant-creator, differing in 23 lines, and is treated as a copy.
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