Agent Skill
Semgrep skill
semgreptrailofbits/skillsplugins/static-analysis/skills/semgrep/SKILL.md
Runs a Semgrep security scan over a codebase: detects languages, selects rulesets, presents the plan for explicit approval, then runs every approved ruleset through scripts/run-scans.sh, which batches the semgrep processes and writes scans.json, and merges the output to SARIF. Supports two scan modes, "run all" for full ruleset coverage and "important only" for security findings at medium-to-high confidence and impact. Uses Semgrep Pro for cross-file taint analysis when it is available. Use when asked to scan code for vulnerabilities, run a security audit with Semgrep, find bugs, or perform static analysis. For the same scan without the approval gate, use the /static-analysis:semgrep-scan workflow.
always on
151 tokname + description
once used
3,434 tokSKILL.md body
bundled files
83 scripts
repo stars
7.7kGitHub
Install the Semgrep skill
Skills CLI (Claude Code, Codex, Cursor and others)
npx skills add https://github.com/trailofbits/skills --skill semgrep
Claude Code, by hand (all projects)
git clone --depth 1 https://github.com/trailofbits/skills.git /tmp/skills mkdir -p ~/.claude/skills cp -R /tmp/skills/plugins/static-analysis/skills/semgrep ~/.claude/skills/semgrep
For one project only, copy the folder into .claude/skills/ in that project instead. The agent picks it up when a task matches its description.
What it costs your context
Agent Skills load in three steps. Tokens counted with the o200k tokenizer; your model's count will differ a little.
| When | What loads | Cost |
|---|---|---|
| Every session | Name and description | 151 tok |
| When the agent uses it | The SKILL.md instructions | 3,434 tok |
| Only if opened | 8 bundled files (112 KB) | varies |
Until it is used, semgrep costs about 9.0× less than the median MCP server we measured (1,362 tokens on every turn). Installing all 97 skills from trailofbits/skills would load 7,555 tokens of descriptions. Skills vs MCP study
Checks
- Ships scripts the agent can run. Read them before installing.
Pre-approved tools (allowed-tools): Bash, Read, Glob, AskUserQuestion, TaskCreate, TaskList, TaskUpdate. The agent can use these without asking while the skill is active.
Checked 2026-10-22 · method
What's inside
The headings of its SKILL.md. Read the full file on GitHub.
- Semgrep Security Scan
- Essential Principles
- When to Use
- When NOT to Use
- Output Directory
- Prerequisites
- Scan Modes
- Orchestration Architecture
- Running it as a Workflow
- Workflow
- Workflow and agents
- Rationalizations to Reject
- Reference Index
- Success Criteria
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