frontmatter-validation

frontmatter-validation is a skill for Claude Code from Everyone-Needs-A-Copilot/claude-copilot. It costs 57 tokens per session (1,476 once invoked), scanned A, original, MIT.

A checker for YAML frontmatter, the metadata block at the top of a Markdown file. It checks required fields, value formats, and document-type rules for skill and documentation files.

In plain words
What is it for?
Use it when auditing or fixing SKILL.md files and other Markdown files with required metadata fields.
Why use it?
It catches incomplete or incorrectly formatted metadata that tools use to find and interpret documentation.

Skill for Claude Code

Written for Claude Code: allowed-tools in frontmatter.

Needs its repository: it reads a path above its own folder, which exists only inside the repository. The line is source_of_truth: ../repo/docs/... # optional, path to canonical doc.

Part of the claude-copilot plugin — 72 skills, 17 commands, 16 agents, 4 hooks shipped together

Install

Getting it into your agent

It runs from inside its repository, so the clone comes first — what it calls does not travel with the file alone.

Clone the repo
git clone --depth 1 https://github.com/Everyone-Needs-A-Copilot/claude-copilot
agentmods
npx agentmods add skills/everyone-needs-a-copilot/claude-copilot/frontmatter-validation

Made for: Claude Code.

Or install claude-copilot, the plugin that ships this one along with the rest of its 72 skills, 17 commands, 16 agents, 4 hooks.

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 frontmatter-validation

README.md
[![agentmods](https://agentmods.dev/badge/skills/everyone-needs-a-copilot/claude-copilot/frontmatter-validation.svg)](https://agentmods.dev/skills/everyone-needs-a-copilot/claude-copilot/frontmatter-validation)
Your own site
<a href="https://agentmods.dev/skills/everyone-needs-a-copilot/claude-copilot/frontmatter-validation"><img src="https://agentmods.dev/badge/skills/everyone-needs-a-copilot/claude-copilot/frontmatter-validation.svg" alt="Measured on agentmods" height="20"></a>
Per session 57 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 1,476 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. Scan, not verified.
Origin original 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 $0.00057 $0.01476
Opus 5 $0.00028 $0.00738
Sonnet 5 $0.00011 $0.00295
Haiku 4.5 $0.00006 $0.00148

Measured yesterday against content hash 89c6190bccd4, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-06, from the pricing page.

Security

Grade A, and why

frontmatter-validation 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 yesterday.

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.

templates/skills/frontmatter-validation/SKILL.md · 195 lines

How it starts

The opening of the file, as written. The whole thing — 195 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Frontmatter Validation

Validate and fix YAML frontmatter metadata in markdown documentation files.

Purpose

Frontmatter enables efficient AI navigation of documentation. This skill ensures all files have correct, complete metadata for their document type.

Frontmatter Schemas by Document Type

Tier 1: Skills (SKILL.md)

---
name: forces-analysis                # required, kebab-case
description: >-                      # required, trigger-rich — used by `cc skill search` for keyword matching
  One-line description covering use cases and when to invoke this skill.
version: 1.2                         # required, semver
allowed-tools: [Read, Write, Edit]   # required, array
tags: [forces, organization]         # required, array
---

Tier 2: Product Documentation

---
product: Insights Copilot            # required
status: active                       # required: active, beta, deprecated
last_updated: 2025-01-15             # required, ISO date
owner: Platform Team                 # required
token_estimate: 650                  # required, integer
doc_type: architecture               # required: overview, architecture, api, integration, security
source_of_truth: ../repo/docs/...    # optional, path to canonical doc
dependencies: [product-a, product-b] # optional, array
summary: Brief description           # optional, 1-2 sentences
key_entities: [Force, Pattern]       # optional, domain entities
integration_endpoints: [POST /api/x] # optional, for API docs
---

Tier 3: Operational Documentation

---
title: Documentation Strategy Guide  # required
doc_type: guide                       # required: guide, standard, reference, runbook
category: operations                  # required: operations, security, development
last_updated: 2025-01-15              # required, ISO date
version: 2.1                          # optional
status: active                        # required: active, deprecated, draft
primary_audience: [developers]        # optional, array
required_reading: false               # optional, boolean
token_estimate: 2500                  # required, integer
replaces: _archive/old-doc.md         # optional, path to replaced doc
related: [other-doc.md]               # optional, array
---

Read the full file on GitHub · 195 lines

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. yesterday First seen · 195 lines · 57 tokens per session scan A 89c6190bccd4

Subscribe to this mod's changes

frontmatter-validation is a skill published in the GitHub repository Everyone-Needs-A-Copilot/claude-copilot (13 stars, last pushed yesterday), licensed MIT. It adds 57 tokens to every session and 1,476 once invoked, about $0.0003 per session on Opus 5. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-09-04.

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