skill-creator

skill-creator is a skill for Claude Code, Codex from tallclub/matimo. It costs 92 tokens per session (3,228 once invoked), scanned A, original, MIT.

A guide and workflow for creating reusable agent skills, which are instruction packages that teach an agent how to handle a particular task. It covers defining when a skill should run, writing its instructions, validating them, and managing its lifecycle in Matimo.

In plain words
What is it for?
Use it to create, edit, improve, validate, and manage skills for recurring workflows or provider-specific tools.
Why use it?
It turns a repeatable process into instructions that can be reused instead of reconstructed each time. Validation helps check that the skill follows the Agent Skills specification.

Skill for Claude CodeCodex

Written for no agent in particular: nothing here depends on one.

Good fit Use it to create, edit, improve, validate, and manage skills for recurring workflows or provider-specific tools.

Compare 6 skills from other repositories ↓
Install with agentmods
npx agentmods add skills/tallclub/matimo/skill-creator
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.

Any agent
npx skills add tallclub/matimo --skill skill-creator
Clone the repo
git clone --depth 1 https://github.com/tallclub/matimo

Made for: Claude Code, Codex.

Wrote 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.

agentmods badge for skill-creator

README.md
[![agentmods](https://agentmods.dev/badge/skills/tallclub/matimo/skill-creator/github.svg)](https://agentmods.dev/skills/tallclub/matimo/skill-creator)
Your own site
<a href="https://agentmods.dev/skills/tallclub/matimo/skill-creator"><img src="https://agentmods.dev/badge/skills/tallclub/matimo/skill-creator/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.

agentmods 80×15 button for skill-creator

Your own site · 80×15
<a href="https://agentmods.dev/skills/tallclub/matimo/skill-creator"><img src="https://agentmods.dev/badge/skills/tallclub/matimo/skill-creator.svg" alt="Reviewed on agentmods" width="80" height="20"></a>
Per session 92 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 3,228 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. A grade says what 26 rules found in the file — not that it is safe. Third-party audits
  • NVIDIA SkillSpector warn 7 Sept 2026
SkillSpector: 1 finding, up to high

These are SkillSpector’s own severities. On a checked sample its high-severity flags on skills were ~96% false positives — a documented command, a public API, a “never do X” rule — so we show them as a caution to read, not a verdict. Why →

  • high Rogue Agent · line 248
    Skill modifies its own code, configuration, or behavior at runtime. Self-modification enables an agent to escalate privileges, disable safety constraints, or install persistent backdoors.
    Fix: Prevent the skill from modifying its own code, SKILL.md, or configuration files. Treat skill files as read-only at runtime.
How audits are shown
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 5.1 $0.00092 $0.03228
Opus 5.5 $0.00037 $0.01291
Sonnet 5.5 $0.00018 $0.00646
Haiku 4.5 $0.00009 $0.00323

Measured 2mo ago against content hash c1436781b8e4, method: parsed. Prices are Anthropic first-party input rates as of 2026-10-07, 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 2mo 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.

python/packages/core/src/matimo/skills/skill-creator/SKILL.md · 440 lines

How it starts

The opening of the file, as written. The whole thing — 440 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Skill Creator

A skill for creating new skills and iteratively improving them in Matimo.

At a high level, creating a skill goes like this:

  1. Understand what the skill should do and when it should trigger
  2. Interview the user to capture requirements and edge cases
  3. Draft the SKILL.md with proper frontmatter and instructions
  4. Validate the skill using matimo_validate_skill
  5. Create the skill using matimo_create_skill
  6. Iterate based on feedback

When to Use This Skill

  • User says "create a skill for X" or "turn this into a skill"
  • User wants to capture a workflow as a reusable pattern
  • User wants to teach agents how to do a specific task
  • User wants to create provider-specific skills for their tools
  • User wants to edit, improve, or validate an existing skill
  • An agent recognizes a repeatable pattern worth capturing

Step 1: Capture Intent

Start by understanding what the user wants. The current conversation might already contain a workflow to capture (e.g., they say "turn this into a skill"). If so, extract answers from the conversation first — the tools used, the sequence of steps, corrections the user made.

Key questions to answer:

  1. What should this skill enable an agent to do? Be specific about the outcome.
  2. When should this skill trigger? What user phrases or contexts should activate it.
  3. Which Matimo tools does it use? These go in the apply-to frontmatter field.
  4. What's the expected workflow? Step-by-step process the agent should follow.
  5. What are the common errors and edge cases? These become the error handling section.

Step 2: Interview and Research

Proactively ask about:

  • Edge cases: What happens when inputs are missing or invalid?
  • Error handling: Which errors are common and how to recover?
  • Best practices: What patterns produce the best results?
  • Anti-patterns: What should agents avoid doing?
  • Dependencies: Does this skill require specific tools or providers?

Read the full file on GitHub · 440 lines

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. 2mo ago First seen · 440 lines · 92 tokens per session scan A c1436781b8e4

Subscribe to this mod's changes

skill-creator is a skill published in the GitHub repository tallclub/matimo (18 stars, last pushed yesterday), licensed MIT. It adds 92 tokens to every session and 3,228 once invoked, about $0.0004 per session on Opus 5.5. 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.

Related

skill-creator compared with skills from other repositories

skill-creator next to 6 skills from other repositories
ModTypeStarsLast pushLicenceScanTokensWorks with
skill-creatortallclub/matimoSkill18yesterdayMITA92Claude Code, Codex
imagegenopenai/codexSkill133kyesterdayApache-2.0A113Codex
playwright-climicrosoft/playwrightSkill99kyesterdayApache-2.0A19Claude Code
local-ai-agentsmicrosoft/ai-agents-for-beginnersSkill79k4d agoMITA200Claude Code, Codex
systematic-debuggingobra/superpowersSkill313k3d agoMITA21Claude Code
next-cache-components-adoptionvercel/next.jsSkill143ktodayMITA95Claude Code
next-partial-prefetching-adoptionvercel/next.jsSkill143ktodayMITA103Claude Code