skill-creator

A guide for creating or updating a Codex skill, which is a set of instructions that helps Codex handle a particular kind of task.

In plain words
What is it for?
It supports planning the scope, instructions, supporting files, and safety boundaries of a new or changed skill.
Why use it?
It helps keep a skill focused on useful decisions without adding unnecessary rules or expanding the user's request.

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

Made for: Claude Code, Codex.

Per session 21 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 2,860 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. Scan, not verified.
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 $0.00021 $0.02860
Opus 5 $0.00010 $0.01430
Sonnet 5 $0.00004 $0.00572
Haiku 4.5 $0.00002 $0.00286

Measured 2d ago against content hash 6656e5475563, 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 2d ago.

The scan reads SKILL.md. This mod also ships 3 executable files (scripts/generate_openai_yaml.py, scripts/init_skill.py, scripts/quick_validate.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.

Origin

Copies of this mod

5 near-identical copies found in the catalogue:

codex-rs/skills/src/assets/samples/skill-creator/SKILL.md · 230 lines

How it starts

The opening of the file, as written. The whole thing — 230 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Skill Creator

Create skills that give Codex useful, non-obvious guidance without constraining unrelated work.

Core Principles

Assume Codex is already capable. Include only information that changes its decisions or improves its work. Remove generic advice, repeated instructions, speculative edge cases, and examples that do not materially clarify the task.

Preserve user intent and scope. A skill should support the requested task, not replace the user's chosen product, expand the assignment, modify unrelated configuration, or imply permission for additional external actions. Do not turn a particular example, past failure, or personal preference into a universal requirement.

Approval to complete a task does not expand its scope or execution permissions. For retrying or externally mutating workflows, define a stopping condition proportional to the risk.

Match specificity to the risk. Give the model room to choose an appropriate approach when multiple approaches are reasonable. Use detailed steps, deterministic scripts, or absolute language only when correctness, safety, permissions, or a genuinely fragile workflow requires them.

For open-ended work, describe the outcome and relevant decision criteria. For workflows with a preferred shape, offer useful examples or configurable scripts. Reserve fixed sequences and narrow parameters for operations where deviation would cause a concrete problem. Preserve non-obvious operational invariants, distinguish actual requirements from optional recommendations or local conventions, and avoid restating policies already enforced elsewhere.

Keep discovery cheap and precise. Skill names and descriptions are available before a skill is loaded. Describe the actual capability and when it applies, adding exclusions only when they prevent likely misrouting. Avoid exhaustive capability lists and catchalls that attract unrelated requests.

Keep skills self-contained; refer to another skill or tool only when the requested workflow genuinely requires it and it is available in the target environment. Specialized review, hardening, or audit workflows should apply when requested or genuinely needed, not merely because ordinary work touches the same subject.

Read the full file on GitHub · 230 lines

Files

What ships with it

8 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.

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. 2d ago First seen · 230 lines · 21 tokens per session scan A 6656e5475563

Subscribe to this mod's changes

skill-creator is a skill published in the GitHub repository openai/codex (120,598 stars, last pushed today), licensed Apache-2.0. It adds 21 tokens to every session and 2,860 once invoked, about $0.0001 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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