missing-frontmatter

A deliberately invalid skill file used to test whether a quality checker detects missing frontmatter, the metadata section some tools expect at the top of a file.

In plain words
What is it for?
Testing quality-checking and provider-adapter snapshot behavior when a skill lacks required metadata.
Why use it?
It provides a known failure case for testing the checker’s structure and naming validation.

Skill for Claude CodeCodex

Install

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.

agentmods
npx agentmods add skills/luongnv89/asm/missing-frontmatter
Any agent
npx skills add luongnv89/asm --skill missing-frontmatter
Clone the repo
git clone --depth 1 https://github.com/luongnv89/asm

Made for: Claude Code, Codex.

Per session 0 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 45 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 $0.00000 $0.00045
Opus 5 $0.00000 $0.00023
Sonnet 5 $0.00000 $0.00009
Haiku 4.5 $0.00000 $0.00005

Measured 2d ago against content hash f313de897127, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

missing-frontmatter 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 2d 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.

tests/fixtures/skills/missing-frontmatter/SKILL.md · 6 lines

What it actually says

Missing frontmatter corpus skill

This skill intentionally has no YAML frontmatter so the static linter fails it on structure and naming. Used as a "fail path" fixture for the quality provider adapter snapshot tests.

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. 2d ago First seen · 6 lines · 0 tokens per session scan A f313de897127

Subscribe to this mod's changes

missing-frontmatter is a skill published in the GitHub repository luongnv89/asm (902 stars, last pushed 3d ago), licensed MIT. It costs nothing until one of its globs matches a file; then it loads 45 tokens. 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 2026-08-30.

Related

Other skills, from other repositories

Skill Development

This skill should be used when the user wants to "create a skill", "add a skill to plugin", "write a new skill", "improve skill description", "organize skill content", or needs guidance on skill structure, progressive disclosure, or skill development best practices for Claude Code plugins.

troykelly/claude-skills · 63 tokens

sentry-setup-ai-monitoring

Setup Sentry AI Agent Monitoring in any project. Use this when asked to add AI monitoring, track LLM calls, monitor AI agents, or instrument OpenAI/Anthropic/Vercel AI/LangChain/Google GenAI. Automatically detects installed AI SDKs and configures the appropriate Sentry integration.

troykelly/claude-skills · 70 tokens

sentry-setup-metrics

Setup Sentry Metrics in any project. Use this when asked to add Sentry metrics, track custom metrics, setup counters/gauges/distributions, or instrument application performance metrics. Supports JavaScript, TypeScript, Python, React, Next.js, and Node.js.

troykelly/claude-skills · 61 tokens

Hook Development

This skill should be used when the user asks to "create a hook", "add a PreToolUse/PostToolUse/Stop hook", "validate tool use", "implement prompt-based hooks", "use ${CLAUDEPLUGINROOT}", "set up event-driven automation", "block dangerous commands", or mentions hook events (PreToolUse, PostToolUse, Stop, SubagentStop…

troykelly/claude-skills · 117 tokens

sentry-setup-logging

Setup Sentry Logging in any project. Use this when asked to add Sentry logs, enable structured logging, setup console log capture, or integrate logging with Sentry. Supports JavaScript, TypeScript, Python, Ruby, React, Next.js, and other frameworks.

troykelly/claude-skills · 61 tokens

sentry-setup-tracing

Setup Sentry Tracing (Performance Monitoring) in any project. Use this when asked to add performance monitoring, enable tracing, track transactions/spans, or instrument application performance. Supports JavaScript, TypeScript, Python, Ruby, React, Next.js, and Node.js.

troykelly/claude-skills · 62 tokens