skill-creator

A tool for creating, editing, improving, and testing coding-agent skills. It can also measure how well a skill performs and improve the wording that determines when it is used.

In plain words
What is it for?
Use it to build a skill from scratch, revise an existing one, run evaluations, compare performance, or improve its triggering description.
Why use it?
It helps turn repeated instructions into reliable skills and exposes problems through testing and performance checks.

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/leonvanzyl/agentic-coding-starter-kit/skill-creator
Any agent
npx skills add leonvanzyl/agentic-coding-starter-kit --skill skill-creator
Clone the repo
git clone --depth 1 https://github.com/leonvanzyl/agentic-coding-starter-kit

Made for: Claude Code, Codex.

Per session 64 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 7,241 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. Scan, not verified.
Origin unknown 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 $0.00064 $0.07241
Opus 5 $0.00032 $0.03621
Sonnet 5 $0.00013 $0.01448
Haiku 4.5 $0.00006 $0.00724

Measured 3d ago against content hash dcd4803e61e9, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

skill-creator 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 3d ago.

The scan reads SKILL.md. This mod also ships 10 executable files (eval-viewer/generate_review.py, scripts/__init__.py, scripts/aggregate_benchmark.py, …), listed below but not scanned — reading those needs a real analyzer, not pattern matching.

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.

.agents/skills/skill-creator/SKILL.md · 486 lines

The source is not reproduced here

No licence file

A repository with no LICENSE is all rights reserved by default, so the body is not copied here. The metadata, the measurements and the link are.

Read it on GitHub

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. 3d ago First seen · 486 lines · 64 tokens per session scan A dcd4803e61e9

Subscribe to this mod's changes

skill-creator is a skill published in the GitHub repository leonvanzyl/agentic-coding-starter-kit (436 stars, last pushed 3mo ago), with no licence file. It adds 64 tokens to every session and 7,241 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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