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.
npx skills add mdsakalu/agent-plugins --skill writing-skillsgit clone --depth 1 https://github.com/mdsakalu/agent-pluginsWrote 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/mdsakalu/agent-plugins/writing-skills)<a href="https://agentmods.dev/skills/mdsakalu/agent-plugins/writing-skills"><img src="https://agentmods.dev/badge/skills/mdsakalu/agent-plugins/writing-skills/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/mdsakalu/agent-plugins/writing-skills"><img src="https://agentmods.dev/badge/skills/mdsakalu/agent-plugins/writing-skills.svg" alt="Reviewed on agentmods" width="80" 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 | $0.00048 | $0.02416 |
| Opus 5 | $0.00024 | $0.01208 |
| Sonnet 5 | $0.00010 | $0.00483 |
| Haiku 4.5 | $0.00005 | $0.00242 |
Grade A, and why
writing-skills 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 9d 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 "https://api.internal-company.com/v2/users" How it starts
The opening of the file, as written. The whole thing — 363 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Writing Skills
Quick Start
Initialize a new skill:
python ~/.claude/skills/writing-skills/scripts/init_skill.py my-skill-name
Or copy this template manually:
---
name: your-skill-name
description: What this skill does and when to use it. Write in third person.
---
# Your Skill Name
## Quick Start
[Minimal working example]
## Instructions
[Clear, step-by-step guidance]
Save as SKILL.md in ~/.claude/skills/your-skill/ or .claude/skills/your-skill/.
Note: Custom slash commands (.claude/commands/) have been merged into skills. Both work identically, but skills support additional features like bundled files and frontmatter options.
Agent Skills Open Standard
Skills follow the agentskills.io open specification, adopted by 25+ AI tools including Claude Code, Cursor, GitHub Copilot, VS Code, and others.
Key concepts:
- Portability: Skills are portable across Claude apps, Claude Code, and API
- Composability: Skills stack together automatically via description matching
- Progressive disclosure: Only load context when needed (token efficiency)
Platform deployment:
| Platform | Discovery | Installation |
|---|---|---|
| Claude Code | Filesystem (~/.claude/skills/) |
Manual or plugin marketplace |
| Claude Apps | Skills UI | Upload or marketplace |
| API | Skills API | Programmatic registration |
Plugin installation (Claude Code):
/plugin marketplace add anthropics/skills
Example skills: github.com/anthropics/skills
Creation Process
1. Understand with Concrete Examples
Before building, gather examples of how the skill will be used:
- "What would a user say to trigger this skill?"
- "What specific tasks should it handle?"
2. Plan Reusable Contents
For each example, identify what would help Claude execute repeatedly:
- Scripts for operations that need deterministic reliability
- References for documentation Claude should consult
- Assets for templates/files used in output
What ships with it
5 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.
- 9d ago First seen · 363 lines · 48 tokens per session scan A 8c792a691c5f
writing-skills is a skill published in the GitHub repository mdsakalu/agent-plugins (4 stars, last pushed 3mo ago), licensed MIT. It adds 48 tokens to every session and 2,416 once invoked, about $0.0002 per session on Opus 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 2026-08-31.
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