skill-guard

The quality gate for Agent Skills.

skill-guard is a CLI tool that validates, secures, and checks Agent Skills, with the default workflow centered on pre-merge repository gates.

The Problem

Agent Skills are powerful. They're also ungoverned. As soon as more than one person contributes skills to a shared agent, things break in hard-to-diagnose ways:

• A new skill's description overlaps with an existing one → agent picks the wrong skill half the time
• Skills with dangerous scripts get merged because nobody reviewed the scripts/ directory
• Nobody knows what skills are installed, who owns them, or whether they still work
• A skill passes every test in isolation but fails when the real agent uses it with 25 other skills loaded

skill-guard is the quality gate that catches these problems before they reach production.

What It Does

ONBOARDING (pre-merge, in CI):
  skill-guard validate   → format compliance + quality scoring
  skill-guard secure     → scan for dangerous patterns
  skill-guard conflict   → detect trigger overlap with existing skills
  skill-guard check      → runs validate + secure + conflict as a single gate

Quick Start

pip install skill-guard

# Initialize in your skills repo
skill-guard init

# Run the default gate
skill-guard check ./skills/my-skill/ --against ./skills/

If you only learn one command, learn check. It is the default pre-merge workflow and the command the GitHub Actions path is built around.

Advanced / Secondary Commands

Use these when you need to inspect one part of the gate in isolation or run non-default workflows:

# Format and metadata quality only
skill-guard validate ./skills/my-skill/

# Security only
skill-guard secure ./skills/my-skill/
skill-guard secure ./skills/my-skill/ --skip-references

# Conflict detection only
skill-guard conflict ./skills/my-skill/ --against ./skills/

Example Output

$ skill-guard validate ./skills/my-skill/

 skill-guard validate — my-skill
┏━━━━━━━━━━━━━━━━━━━━━━━━━━━┳━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━┓
┃ Check                     ┃ Result                                           ┃
┡━━━━━━━━━━━━━━━━━━━━━━━━━━━╇━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━┩
│ skill_md_exists           │ ✅ SKILL.md found                                │
│ valid_yaml_frontmatter    │ ✅ Valid YAML frontmatter                        │
│ name_field_present        │ ✅ name: my-skill                                │
│ description_field_present │ ✅ description field present                     │
│ directory_name_matches    │ ✅ Directory name matches skill name             │
│ description_trigger_hint  │ ✅ Description contains trigger hint ('Use when')│
│ no_broken_body_paths      │ ✅ No broken relative paths in SKILL.md body     │
│ evals_directory_exists    │ ⚠️ No evals/ directory found                     │
│                           │ → Create evals/evals.json or evals/config.yaml   │
│ metadata_has_author       │ ✅ author: my-team                               │
│ metadata_has_version      │ ✅ version: 1.0                                  │
└───────────────────────────┴──────────────────────────────────────────────────┘
Score: 97/100 | Grade: A | Blockers: 0 | Warnings: 1

Prerequisites

Note: every skill-guard command works fully offline — no agent or API key needed.

The default offline path is already useful on its own: validate catches structure and metadata problems, secure catches risky patterns with remediation hints, conflict flags overlapping triggers, and check combines those static gates into one pre-merge decision.

Installation

# Core (static analysis — no agent required)
pip install skill-guard

# Optional embeddings support
pip install skill-guard[embeddings]

# Optional LLM-based conflict detection
pip install skill-guard[llm]

Conflict Detection Modes

# TF-IDF (default)
skill-guard conflict ./skills/my-skill/ --against ./skills/ --method tfidf

# Embeddings-based overlap detection
skill-guard conflict ./skills/my-skill/ --against ./skills/ --method embeddings

# Choose a different embeddings model
skill-guard conflict ./skills/my-skill/ --against ./skills/ --method embeddings --model all-MiniLM-L12-v2

# Offline embeddings (local model only; no downloads)
skill-guard conflict ./skills/my-skill/ --against ./skills/ --method embeddings \
  --model-path /models/all-MiniLM-L6-v2 --offline

# LLM-based overlap detection
export OPENAI_API_KEY=...
skill-guard conflict ./skills/my-skill/ --against ./skills/ --method llm

embeddings uses the all-MiniLM-L6-v2 sentence-transformers model by default (override with --model, --model-path, or conflict.embeddings_model/conflict.embeddings_model_path) and caches downloads under conflict.embeddings_cache_dir (default .skill-guard-cache/embeddings/). On first download, it prints a "Downloading model..." message to stderr. Use --offline to require a local/cached model and skip downloads. llm uses the OpenAI Chat API with gpt-4o-mini by default.

Ignoring known conflicts

Add conflict_ignore to your SKILL.md frontmatter to skip comparisons against specific skills:

---
name: my-skill
description: "Use when ..."
conflict_ignore:
  - legacy-skill
  - skills/legacy-skill/SKILL.md
---

Documentation

• Getting Started
• CI/CD Integration
• Configuration Reference
• Automation Policy
• Release Gate Checklist
• Roadmap

Anthropic Spec Validation

skill-guard validate includes Anthropic AgentSkills spec compliance checks by default. Set validate.anthropic_spec: false in skill-guard.yaml if you need to disable those additional findings.

Exit Codes

• 0: success
• 1: validation/security failures
• 2: warnings only (when fail_on_warning is false)
• 3: config error
• 4: parse error

Pre-commit

Use pre-commit to enforce checks before skill changes land:

repos:
  - repo: https://github.com/vaibhavtupe/skill-guard
    rev: v0.9.0
    hooks:
      - id: skill-guard-validate
      - id: skill-guard-secure
      - id: skill-guard-check

These hooks run against changed SKILL.md files, deduplicate by skill root, and then execute the corresponding skill-guard command for each affected skill.

Templates

Use skill-guard init --template base to scaffold a new skill, or skill-guard init --list-templates to see the available scaffolds. Generated templates include SKILL.md, evals/evals.json, references/, scripts/, and assets/ so they validate immediately.

GitHub Actions

name: skill-guard PR Gate

on:
  pull_request:
    paths:
      - "skills/**"

jobs:
  skill-guard:
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v4
      - uses: actions/setup-python@v5
        with:
          python-version: "3.12"
      - run: python -m pip install skill-guard
      - run: |
          skill-guard check skills/ \
            --changed \
            --base-ref "${{ github.event.pull_request.base.sha }}" \
            --head-ref "${{ github.sha }}" \
            --format md > skill-guard-summary.md

See docs/ci-integration.md for the canonical workflow, JSON + markdown artifact strategy, and the checked-in example at .github/workflows/skill-guard-pr-gate.yml.

What skill-guard Does NOT Do

• Does not replace Anthropic's skill-creator for writing skills
• Does not host or serve skills — skills live in your repo
• Does not modify skills — it reports issues, authors fix them
• Does not require a database or server — everything runs from files in your repo

Contributing

See CONTRIBUTING.md. We welcome contributions of all kinds.

For planning and release discipline:

• ROADMAP.md is the canonical scope source
• docs/automation-policy.md defines PM ↔ Dev workflow
• docs/release-gate.md is the required pre-release checklist

License

Apache 2.0. See LICENSE.