Semgrep

What it does

When your agent uses it

• Asked to scan code for vulnerabilities
• Run a security audit with Semgrep
• Perform static analysis

Example prompts

• “run all”
• “important only”
• “/semgrep”

Requirements

• Python 3
• Docker
• Pre-approved tools (allowed-tools): Bash, Read, Glob, Task, AskUserQuestion, TaskCreate, TaskList, TaskUpdate

Workflow steps

5 steps, taken from the first numbered list in SKILL.md.

1. 1Always use --metrics=off — Semgrep sends telemetry by default; --config auto also phones home. Every semgrep command must include…
2. 2User must approve the scan plan (Step 3 is a hard gate) — The original "scan this codebase" request is NOT approval. Present exact…
3. 3Third-party rulesets are required, not optional — Trail of Bits, 0xdea, and Decurity rules catch vulnerabilities absent from the official…
4. 4Spawn all scan Tasks in a single message — Parallel execution is the core performance advantage. Never spawn Tasks sequentially; always…
5. 5Always check for Semgrep Pro before scanning — Pro enables cross-file taint tracking and catches ~250% more true positives. Skipping the…

What it can do on your machine

Read from SKILL.md and the folder at commit 9ffdcac. It shows what the files ask for, not the result of running them.

• Tool permissions

  Pre-approves these tools, so the agent can use them without asking each time:

  • Bash
  • Read
  • Glob
  • Task
  • AskUserQuestion
  • TaskCreate
  • TaskList
  • TaskUpdate

  From allowed-tools in the SKILL.md frontmatter.

• Runs code

  Ships 1 file in scripts/ (Python), which the agent can run.

  Shell commands in SKILL.md call:

  • semgrep
  • uv

  From the folder's file list and the shell code blocks in SKILL.md.

• Network

  Links to these hosts (documentation or services it may open):

  • semgrep.dev

  From URLs in SKILL.md, links to its own repository left out.

• Credentials

  Names no API keys, tokens, secrets or passwords.

  From names ending in _API_KEY, _TOKEN, _SECRET, _KEY or _PASSWORD in SKILL.md.

Context cost

Semgrep loads about 2.4k tokens when it runs, and up to ~7k if it reads all its reference files. Until then it costs about 118 tokens; SKILL.md has 895 words of instructions outside code blocks.

Always · name and description, kept in context so the agent knows when to use it

~118

When it runs · the whole SKILL.md, loaded when a task matches

~2.4k

With references · SKILL.md plus every file in references/, read only if the agent opens them

~7k

Estimates: characters ÷ 4, the usual rule of thumb; real counts depend on the model's tokenizer. Scripts and assets cost tokens only if the agent reads them.

Safety

• NotePre-approves every shell command (allowed-tools: Bash)SKILL.md

  allowed-tools: Bash, Read, Glob, Task, AskUserQuestion, TaskCreate, TaskList, TaskUpdate

Automated static check — not a guarantee. Review scripts before installing. It scans the text of SKILL.md for risky patterns (piping downloads into a shell, reading credential files, hidden Unicode, destructive commands); the scripts in this folder are not scanned.

SKILL.md

The full file from vigolium/piolium at commit 9ffdcac, republished under its MIT licence (© vigolium). 895 words, ~2,430 tokens.

name

semgrep

description

Run Semgrep static analysis scan on a codebase using parallel subagents. Supports two scan modes — "run all" (full ruleset coverage) and "important only" (high-confidence security vulnerabilities). Automatically detects and uses Semgrep Pro for cross-file taint analysis when available. Use when asked to scan code for vulnerabilities, run a security audit with Semgrep, find bugs, or perform static analysis. Spawns parallel workers for multi-language codebases.

allowed-tools

Bash, Read, Glob, Task, AskUserQuestion, TaskCreate, TaskList, TaskUpdate

# Resolve output directory
if [ -n "$USER_SPECIFIED_DIR" ]; then
  OUTPUT_DIR="$USER_SPECIFIED_DIR"
else
  BASE="static_analysis_semgrep"
  N=1
  while [ -e "${BASE}_${N}" ]; do
    N=$((N + 1))
  done
  OUTPUT_DIR="${BASE}_${N}"
fi
mkdir -p "$OUTPUT_DIR/raw" "$OUTPUT_DIR/results"

$OUTPUT_DIR/
├── rulesets.txt                 # Approved rulesets (logged after Step 3)
├── raw/                         # Per-scan raw output (unfiltered)
│   ├── python-python.json
│   ├── python-python.sarif
│   ├── python-django.json
│   ├── python-django.sarif
│   └── ...
└── results/                     # Final merged output
    └── results.sarif

semgrep --pro --validate --config p/default 2>/dev/null && echo "Pro available" || echo "OSS only"

┌──────────────────────────────────────────────────────────────────┐
│ MAIN AGENT (this skill)                                          │
│ Step 1: Detect languages + check Pro availability                │
│ Step 2: Select scan mode + rulesets (ref: rulesets.md)           │
│ Step 3: Present plan + rulesets, get approval [⛔ HARD GATE]     │
│ Step 4: Spawn parallel scan Tasks (approved rulesets + mode)     │
│ Step 5: Merge results and report                                 │
└──────────────────────────────────────────────────────────────────┘
         │ Step 4
         ▼
┌─────────────────┐
│ Scan Tasks      │
│ (parallel)      │
├─────────────────┤
│ Python scanner  │
│ JS/TS scanner   │
│ Go scanner      │
│ Docker scanner  │
└─────────────────┘

uv run {baseDir}/scripts/merge_sarif.py $OUTPUT_DIR/raw $OUTPUT_DIR/results/results.sarif

© vigolium, MIT. Rendered from Markdown: HTML in the file is shown as text, images as links, and headings moved down two levels. Raw file

Files

SKILL.md and 5 other files (scripts, references) in skills/semgrep of vigolium/piolium.

• SKILL.md
• references/rulesets.md
• references/scan-modes.md
• references/scanner-task-prompt.md
• scripts/merge_sarif.py
• workflows/scan-workflow.md

Open the folder on GitHubat commit 9ffdcac

Used in 1 other repository

We found 1 copy of this SKILL.md (exact, near-identical or edited) in other folders, from 1 other GitHub owner. This page covers the copy in vigolium/piolium, which our catalogue first saw on October 7, 2026.

• CraftOS-dev/CraftBotskills/semgrep