aigent-validator

A checker for SKILL.md files, which are instruction files that define skills for AI agents. It compares their names, descriptions, formatting, and content rules with Anthropic's published skill specification.

In plain words
What is it for?
Use it to review a new or changed agent skill and report errors or warnings about its structure and wording.
Why use it?
It finds specification problems before a skill is used or shared. If the checking command is unavailable, it provides rules for checking the file by hand.

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/wkusnierczyk/aigent/aigent-validator
Any agent
npx skills add wkusnierczyk/aigent --skill aigent-validator
Clone the repo
git clone --depth 1 https://github.com/wkusnierczyk/aigent

Made for: Claude Code, Codex.

Per session 59 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 424 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 $0.00059 $0.00424
Opus 5 $0.00030 $0.00212
Sonnet 5 $0.00012 $0.00085
Haiku 4.5 $0.00006 $0.00042

Measured 2d ago against content hash 3fd60a22faca, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

aigent-validator 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.

skills/aigent-validator/SKILL.md · 62 lines

What it actually says

Skill Validator

Setup

Check if aigent is available:

command -v aigent

With aigent CLI

If aigent is on $PATH, use the CLI for authoritative validation:

aigent validate <skill-directory>

Exit code 0 means valid. Non-zero means errors. Warnings are printed but do not cause failure.

If a SKILL.md file path is provided instead of a directory, aigent automatically resolves to the parent directory.

Without aigent CLI

If aigent is not available, validate manually by reading the SKILL.md and checking these rules:

Frontmatter checks

  1. File starts and ends with --- delimiters
  2. name field: present, string, ≤ 64 chars, lowercase + hyphens + numbers only, no consecutive hyphens, no leading/trailing hyphens, no reserved words ("anthropic", "claude"), no XML tags, matches directory name
  3. description field: present, string, non-empty, ≤ 1024 chars, no XML tags

Optional field checks

  1. compatibility: if present, string, ≤ 500 chars
  2. license: if present, string
  3. allowed-tools: if present, string

Body checks

  1. Body ≤ 500 lines (warning, not error)

Report format

Report each issue on its own line. Prefix warnings with "warning: ".

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 · 62 lines · 59 tokens per session scan A 3fd60a22faca

Subscribe to this mod's changes

aigent-validator is a skill published in the GitHub repository wkusnierczyk/aigent (4 stars, last pushed 6mo ago), licensed Apache-2.0. It adds 59 tokens to every session and 424 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 2026-08-31.

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