create-skill

A guide for creating a reusable coding-agent skill from a workflow you repeat. It interviews you, documents the process, tests the result on a real example, and installs it.

In plain words
What is it for?
It helps define a repeatable task, identify its failure modes, write a SKILL.md file, test the skill, and make it available for future requests.
Why use it?
It turns personal know-how into consistent instructions instead of requiring you to explain the same process each time. It also captures common mistakes and what a correct result looks like.

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/sethgammon/citadel/create-skill
Any agent
npx skills add SethGammon/Citadel --skill create-skill
Clone the repo
git clone --depth 1 https://github.com/SethGammon/Citadel

Made for: Claude Code, Codex.

Per session 73 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 1,819 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 $0.00073 $0.01819
Opus 5 $0.00036 $0.00910
Sonnet 5 $0.00015 $0.00364
Haiku 4.5 $0.00007 $0.00182

Measured yesterday against content hash 2d348d40866e, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

create-skill 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 yesterday.

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.

skills/create-skill/SKILL.md · 215 lines

How it starts

The opening of the file, as written. The whole thing — 215 lines — stays where its author put it; the contents beside it link to each section on GitHub.

/create-skill — Skill Creator

Orientation

Use when:

  • The user says "I keep doing this same thing" or "automate this for me"
  • The user wants to encode a workflow they have refined through repetition
  • The user says "create a skill for X" or "make a skill that does Y"

Do NOT use when:

  • The user wants a one-off task done (just do it)
  • The pattern has only happened once
  • An existing skill already covers this
  • The user wants to modify an existing skill (edit directly)

Output: A complete .claude/skills/{name}/SKILL.md in the project directory, tested and working.

Protocol

Step 1: DISCOVER — The Three Questions

Ask these three questions and wait for answers before proceeding.

Q1: "What do you keep repeating?" Listen for: trigger, steps in order, scope, frequency. If vague, probe: "Walk me through the last time you did this."

Q2: "What mistakes happen when you do it manually?" Listen for: forgotten steps, ordering mistakes, convention drift, edge cases. These become guardrails and quality gates.

Q3: "What does 'done right' look like?" Listen for: observable outputs, quality signals, anti-patterns. These become quality gates and exit protocol.

Step 2: ANALYZE — Extract the Skill's DNA

Internal working material — do not show to user.

2a. Identity statement: "You are a {role} that {does what} to ensure {outcome}." Must distinguish this skill from all others.

2b. Trigger keywords (5-10): Specific enough to avoid false matches. Check existing .claude/skills/ for conflicts.

2c. Protocol steps: Transform "what I do" into numbered steps where:

  • Each step has a clear input and output
  • Decision points have explicit criteria ("IF x THEN y, ELSE z")
  • Steps reference concrete things (file paths, commands, patterns)

Bad: "3. Review the code for issues." Good: "3. Read every function. For each, check: (a) return type explicit, (b) error cases handled, (c) no input mutations. List violations with line numbers."

Read the full file on GitHub · 215 lines

Files

What ships with it

2 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. yesterday First seen · 215 lines · 73 tokens per session scan A 2d348d40866e

Subscribe to this mod's changes

create-skill is a skill published in the GitHub repository SethGammon/Citadel (912 stars, last pushed 4d ago), licensed MIT. It adds 73 tokens to every session and 1,819 once invoked, about $0.0004 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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