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.
git clone --depth 1 https://github.com/stackhawk/agent-skillsnpx agentmods add skills/stackhawk/agent-skills/skill-authoringWrote 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.
[](https://agentmods.dev/skills/stackhawk/agent-skills/skill-authoring)<a href="https://agentmods.dev/skills/stackhawk/agent-skills/skill-authoring"><img src="https://agentmods.dev/badge/skills/stackhawk/agent-skills/skill-authoring/github.svg" alt="Measured on agentmods" height="20"></a>Or the 80×15 button, for a site that already has a row of RSS and ATOM ones. Only the verdict fits; the numbers stay here.
<a href="https://agentmods.dev/skills/stackhawk/agent-skills/skill-authoring"><img src="https://agentmods.dev/badge/skills/stackhawk/agent-skills/skill-authoring.svg" alt="Reviewed on agentmods" width="80" height="20"></a>- NVIDIA SkillSpector pass
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.
| Model | Per session | Once invoked |
|---|---|---|
| Fable 5.1 | $0.00085 | $0.02124 |
| Opus 5.5 | $0.00034 | $0.00850 |
| Sonnet 5.5 | $0.00017 | $0.00425 |
| Haiku 4.5 | $0.00009 | $0.00212 |
Grade A, and why
skill-authoring scanned grade A with 1 finding against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 1mo ago.
A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.
Makes network callslowCapability
Not a fault in itself. Listed so you know the mod talks to something, and to what.
`curl "$HOST<spec-path>"` over `curl "$HOST/authors"` — a literal paste of the placeholder How it starts
The opening of the file, as written. The whole thing — 255 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Skill Authoring Guide
This skill documents the rules for creating and maintaining agent skills in
the stackhawk/agent-skills repository.
Authoring Rules (Quick Reference)
These are the non-negotiable rules. CI validates them on every PR.
| Rule | Requirement |
|---|---|
| SKILL.md length | Body ≤ 500 lines (excluding frontmatter) |
| Frontmatter | name:, version:, description: all required |
| Description | Third person; max 1024 characters |
| Reference files | All linked from SKILL.md; must not link to each other |
| Reference ToC | Required when file > 100 lines |
| Progressive disclosure | Summary + link in SKILL.md; detail in references/ |
SKILL.md Rules
Frontmatter
Every SKILL.md must open with a YAML frontmatter block:
---
name: <skill-name> # matches the plugin directory name and symlink folder name
version: <semver> # kept in sync by bump-version.sh
description: > # third person; max 1024 characters; describes when to trigger
...
---
Description writing rules:
- Third person ("Guides authoring...", not "I help you author...")
- Opens with what the skill does (verb phrase)
- Includes "Use when" trigger conditions
- Includes "Do NOT trigger for" exclusions
- Max 1024 characters — CI rejects longer descriptions
Body length
The SKILL.md body (everything after frontmatter) must stay at or under 500 lines. Use the progressive disclosure pattern to stay within this limit:
- Keep decision logic, commands, and critical rules in SKILL.md
- Move deep detail to
references/*.mdfiles and link them from SKILL.md - Link format:
→ [references/filename.md](references/filename.md)
What belongs in SKILL.md
- Trigger/skip conditions (when to run, when to stop)
- Step-by-step orchestration logic the agent follows
- Decision tables and critical rules
- Commands the agent runs directly
- Links to reference files (one line per link)
What belongs in references/
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.
- 1mo ago Changed e07c9d968dc8
- 1mo ago First seen · 255 lines · 85 tokens per session scan A 4508d4bd9d76
skill-authoring is a skill published in the GitHub repository stackhawk/agent-skills (16 stars, last pushed 8d ago), licensed MIT. It adds 85 tokens to every session and 2,124 once invoked, about $0.0003 per session on Opus 5.5. A static security scan graded it A with 1 finding (makes network calls). No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-30.
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