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Agent skill

Frontmatter Guard

by inbrainfun in inbrainfun/inbrain

Validate and auto-repair YAML frontmatter on brain pages. An agent skill from inbrainfun/inbrain.

Custom licenceAuto-check passed

Install Frontmatter Guard

skills CLI
$ npx skills add inbrainfun/inbrain --skill frontmatter-guard -a claude-code

Project install by default; add -g for ~/.claude/skills/.

GitHub CLI
$ gh skill install inbrainfun/inbrain frontmatter-guard --agent claude-code

Project scope by default; add --scope user for a personal install. Needs GitHub CLI 2.90.0 or later (public preview).

Manual copy
$ git clone --depth 1 https://github.com/inbrainfun/inbrain.git skills-src && mkdir -p .claude/skills && cp -r skills-src/skills/frontmatter-guard .claude/skills/frontmatter-guard && rm -rf skills-src

Use ~/.claude/skills/ instead of .claude/skills for a personal install. The folder must contain SKILL.md.

Claude Code skills documentation · loads skills from .claude/skills/

Facts

Skill name
frontmatter-guard
GitHub stars
142
Token cost
~2.4k tokens
SKILL.md length
1,018 words
Files
2
Skills in repo
52
Repo updated
First seen
Licence
Custom licence

At a glance

Validate and auto-repair YAML frontmatter on brain pages. An agent skill from inbrainfun/inbrain.

  • Works in 4 steps: Audit → Validate one path → Fix → …
  • SKILL.md covers Contract, Why This Exists, Validation classes and Phases, plus 6 more sections
  • Calls git

What it does

Frontmatter Guard is an agent skill from inbrainfun/inbrain. Validate and auto-repair YAML frontmatter on brain pages. Catches malformed pages before they enter the brain (missing closing ---, nested quotes, slug mismatches, null bytes, empty frontmatter, YAML parse failures). Wraps the inbrain frontmatter CLI for agent-driven workflows.

Its SKILL.md is about 2.4k tokens, which your agent loads only when the skill is triggered. The skill folder holds 1 other file.

Example prompts

  • “/frontmatter-guard”

Workflow steps

4 steps, taken from the step headings in SKILL.md.

  1. Audit
  2. Validate one path
  3. Fix
  4. Pre-commit hook (optional)

What it can do on your machine

Read from SKILL.md and the folder at commit 5231990. It shows what the files ask for, not the result of running them.

  • Tool permissions

    Pre-approves nothing: there is no allowed-tools line, so your agent's usual permission prompts apply.

    From allowed-tools in the SKILL.md frontmatter.

  • Runs code

    Shell commands in SKILL.md call:

    • git

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

  • Network

    No URLs in SKILL.md. Its commands use git, which can reach the network depending on how they are called.

    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

Frontmatter Guard loads about 2.4k tokens when it runs. Until then it costs about 75 tokens; SKILL.md has 1,018 words of instructions outside code blocks.

Always · name and description, kept in context so the agent knows when to use it
~75
When it runs · the whole SKILL.md, loaded when a task matches
~2.4k

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

Auto-check passed

The automated check found no risky patterns in SKILL.md.

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); files beside SKILL.md are not scanned.

SKILL.md

Its licence (Custom licence) doesn't allow us to republish the file, so here is its outline and opening line. It has 1,018 words (~2,414 tokens).

name
frontmatter-guard
version
1.0.0
triggers
validate frontmatter, check frontmatter, fix frontmatter, frontmatter audit, brain lint
tools
exec
mutating
true

Read the full SKILL.md on GitHub

Files

SKILL.md and 1 other file in skills/frontmatter-guard of inbrainfun/inbrain.

  • SKILL.md
  • routing-eval.jsonl

Open the folder on GitHubat commit 5231990

Compare with similar skills

Frontmatter Guard next to the 5 skills that share the most tags, products or categories with it. Stars are the repository's; “used in” counts other GitHub owners with a copy.

Frontmatter Guard compared with similar skills
SkillStarsUsed inTokensAuto-checkLicenceRepo updated
Frontmatter Guard this skillinbrainfun/inbrain142—~2.4kAutomated safety check: PassCustom licence
Frontmatter Guardgarrytan/gbrain31k—~3.8kAutomated safety check: PassMIT
Frontmatter RepairLearnPrompt/LearnPrompt2.7k—~212Automated safety check: PassCustom licence
Safety Guardaffaan-m/ECC276k2 repos~554Automated safety check: NotesMIT
Guard Modegarrytan/gstack136k—~1kAutomated safety check: NotesMIT
Openclaw Repair Sweepopenclaw/openclaw392k—~1.8kAutomated safety check: PassMIT

Similar skills

  • Frontmatter Guard

    garrytan/gbrain

    Validate and auto-repair YAML frontmatter on brain pages. An agent skill from garrytan/gbrain.

    31k GitHub stars~3.8k tokensUpdated today
    Auto-check passed

  • Frontmatter Repair

    LearnPrompt/LearnPrompt

    Repair synthetic MDX frontmatter when title, description, or sidebar.order drift from the frontmatter contract.

    2.7k GitHub stars~212 tokensUpdated yesterday
    Documents & OfficeAuto-check passed

  • Safety Guard

    affaan-m/ECC

    Guard against destructive operations with three modes: Careful intercepts dangerous commands (rm -rf, git push --force, DROP TABLE) for confirmation, Freeze locks writes to one directory, and Guard…

    276k GitHub starsUsed in 2 repos~554 tokens
    DevelopmentAuto-check: notes

  • Guard Mode

    garrytan/gstack

    Switches on full safety by combining warnings before destructive commands with a block on edits outside one directory you choose, for work on production or live systems.

    136k GitHub stars~1k tokensUpdated today
    Agent WorkflowsAuto-check: notes

  • Openclaw Repair Sweep

    openclaw/openclaw

    Run scoped OpenClaw issue/PR repair campaigns: coordinate workers, prove root causes, and land or close verified work under the requested authority.

    392k GitHub stars~1.8k tokensUpdated today
    DevelopmentAuto-check passed

  • TDD Repair

    ruvnet/ruflo

    Test-Driven Repair — given a failing test, spawn a bounded headless claude -p (Read/Edit/Bash only) that makes the test pass without modifying it.

    74k GitHub stars~1.6k tokensUpdated today
    Testing & QAAuto-check: notes

More from inbrainfun/inbrain

All 52 skills in this repo

  • Academic Verify

    inbrainfun/inbrain

    Verify a research claim or academic citation by tracing it through publication → methodology → raw data → independent replication.

    142 GitHub starsUsed in 1 repo~2.3k tokens
    Auto-check passed

  • Cold Start

    inbrainfun/inbrain

    Day-one data bootstrapping for a new brain. An agent skill from inbrainfun/inbrain.

    142 GitHub starsUsed in 1 repo~4.7k tokens
    Auto-check passed

  • Enrich

    inbrainfun/inbrain

    Enrich brain pages with tiered enrichment protocol. An agent skill from inbrainfun/inbrain.

    142 GitHub starsUsed in 1 repo~2.8k tokens
    Auto-check passed

  • Idea Lineage

    inbrainfun/inbrain

    Trace one idea's evolution through the brain: first mention, best articulation, related concepts, reversals, contradictions, abandoned branches, and the current live version.

    142 GitHub starsUsed in 1 repo~2.2k tokens
    Auto-check passed

  • Maintain

    inbrainfun/inbrain

    Brain health checks: back-link enforcement, citation audit, filing validation, stale info detection, orphan pages, and benchmarks.

    142 GitHub starsUsed in 1 repo~4.4k tokens
    Auto-check passed

  • Schema Author

    inbrainfun/inbrain

    Evolve your brain's schema pack. An agent skill from inbrainfun/inbrain.

    142 GitHub starsUsed in 1 repo~3.3k tokens
    Auto-check passed

Questions about Frontmatter Guard

What does Frontmatter Guard do?

Validate and auto-repair YAML frontmatter on brain pages. An agent skill from inbrainfun/inbrain. Frontmatter Guard is an agent skill from inbrainfun/inbrain. Validate and auto-repair YAML frontmatter on brain pages.

How do I install Frontmatter Guard in Claude Code?

Run `npx skills add inbrainfun/inbrain --skill frontmatter-guard -a claude-code`. Or copy the skill folder (skills/frontmatter-guard in inbrainfun/inbrain) into .claude/skills/frontmatter-guard in your project. Claude Code loads it when a task matches its description.

How do I install Frontmatter Guard in Codex?

Run `npx skills add inbrainfun/inbrain --skill frontmatter-guard -a codex`. Or copy the skill folder (skills/frontmatter-guard in inbrainfun/inbrain) into .agents/skills/frontmatter-guard in your project. Codex loads it when a task matches its description.

Can I use Frontmatter Guard in Cursor, Gemini CLI or GitHub Copilot?

Cursor, Gemini CLI, GitHub Copilot and OpenCode also load SKILL.md folders. With the skills CLI, run `npx skills add inbrainfun/inbrain --skill frontmatter-guard -a cursor` (or -a gemini-cli, github-copilot or opencode for the others). To copy it by hand, put the folder in .cursor/skills/frontmatter-guard, .gemini/skills/frontmatter-guard, .github/skills/frontmatter-guard and .opencode/skills/frontmatter-guard in your project.

What does Frontmatter Guard need to run?

Going by SKILL.md and its folder, Frontmatter Guard needs the command-line tools its instructions call (git).

Does Frontmatter Guard access the network?

SKILL.md contains no URLs. Its commands use git, which can reach the network depending on how they are called. This is read from the text; nothing was executed.

Is Frontmatter Guard safe to install?

Our automated static check of SKILL.md found no risky patterns, such as piping downloads into a shell, reading credential files or hidden Unicode. It is not a guarantee. Review the folder before installing.

What licence does Frontmatter Guard use?

Frontmatter Guard has a licence file (the repository's licence) that doesn't match a standard licence. Read it on GitHub before reusing the skill.

How many tokens does Frontmatter Guard use?

About 2.4k tokens (SKILL.md is roughly 9.7k characters). Agents keep only the skill's name and description in context until a task matches; then they load SKILL.md in full.

What are the alternatives to Frontmatter Guard?

Skills that share tags, products or a category with Frontmatter Guard: Frontmatter Guard (garrytan/gbrain, 31k stars), Frontmatter Repair (LearnPrompt/LearnPrompt, 2.7k stars), Safety Guard (affaan-m/ECC, 276k stars) and Guard Mode (garrytan/gstack, 136k stars). The comparison table on this page puts their stars, adoption, token cost, safety result and licence side by side.

Who maintains Frontmatter Guard?

inbrainfun (a GitHub user) maintains it in inbrainfun/inbrain, which has 142 GitHub stars. The repository holds 52 skills in this directory. The repository was last updated on July 17, 2026.

Source: inbrainfun/inbrain on GitHub. Facts on this page come from the repository at the commit we read; the author's words are quoted as theirs.