Borrowing it
Nothing to install: this file belongs to houarnu166/skillful-agent-system-builder. Take a copy, put it at the same path in your own repository, and replace the rules that are about this project with yours.
curl -O https://raw.githubusercontent.com/houarnu166/skillful-agent-system-builder/main/.agents/skills/skill-design/SKILL.mdgit clone --depth 1 https://github.com/houarnu166/skillful-agent-system-builderWrote 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/houarnu166/skillful-agent-system-builder/skill-design)<a href="https://agentmods.dev/skills/houarnu166/skillful-agent-system-builder/skill-design"><img src="https://agentmods.dev/badge/skills/houarnu166/skillful-agent-system-builder/skill-design.svg" alt="Measured on agentmods" height="20"></a>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 | $0.00062 | $0.01143 |
| Opus 5 | $0.00031 | $0.00571 |
| Sonnet 5 | $0.00012 | $0.00229 |
| Haiku 4.5 | $0.00006 | $0.00114 |
Grade A, and why
skill-design 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 7d 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.
How it starts
The opening of the file, as written. The whole thing — 157 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Skill Design Guide
Overview
This Skill provides methods for designing and implementing effective Skills. Skills are modular packages that extend Claude's capabilities for specific domains or tasks.
About Skills
Skills are modular, self-contained packages that extend Claude's capabilities by providing specialized knowledge, workflows, and tools. Think of them as "onboarding guides" for specific domains or tasks.
What Skills provide:
- Specialized workflows - Multi-step procedures for specific domains
- Tool integrations - Guides for specific file formats or API operations
- Domain expertise - Company-specific knowledge, schemas, business logic
- Bundled resources - Scripts, reference documents, assets for complex and repetitive tasks
Core Principle: Concise is Key
Context window is a public good. Only add context Claude doesn't already know.
- "Does Claude really need this explanation?"
- "Does this paragraph justify its token cost?"
Prefer concise examples over verbose explanations.
Skill Creation Process (6 Steps)
Step 1: Understand with Concrete Examples
Collect and understand concrete examples of how the Skill will be used.
Step 2: Plan Reusable Content
Identify reusable resources that can be separated into scripts, references, assets.
Step 3: Initialize Skill
Create Skill directory structure. (Recommend using init_skill.py script)
Step 4: Write Skill
Implement SKILL.md and bundled resources. → See frontmatter-guide.md for frontmatter rules
Step 5: Package Skill
Package into distributable .skill file. (Use package_skill.py)
Step 6: Iterate with Real Usage
Improve based on actual usage.
SKILL.md Structure
skill-name/
├── SKILL.md (required)
│ ├── YAML frontmatter (name, description)
│ └── Markdown instructions
└── Bundled Resources (optional)
├── scripts/ - Executable code
├── references/ - Documents loaded when needed
└── assets/ - Files used in output
What ships with it
4 files beside SKILL.md in the same directory: the scripts, references and assets a skill reads on demand. Not counted in the per-session cost; read them before you install if any of them is executable.
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.
- 7d ago First seen · 157 lines · 62 tokens per session scan A 3eb0b31b80a3
skill-design is a skill published in the GitHub repository houarnu166/skillful-agent-system-builder (23 stars, last pushed 7mo ago), licensed MIT. It adds 62 tokens to every session and 1,143 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 2026-08-30.
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