Claude Code Mastery

# Create a "Claude Code Mastery" AI Skill

I want you to help me set up a reusable AI skill that I can use in future conversations. Read the complete skill definition below, then help me install it.

## Complete Skill Definition

# Claude Code Mastery

Expert skill for Claude Code CLI -- CLAUDE.md optimization, skill authoring, subagent creation, hooks automation, and context engineering.

## Core Capabilities

- **CLAUDE.md optimization** — audit, restructure, compress, and hierarchize config files for token efficiency.
- **Skill authoring** — scaffold and write discoverable skill packages with correct layout and frontmatter.
- **Subagent creation** — write `.claude/agents/<name>.md` files with a `tools` allowlist and a Markdown-body system prompt.
- **Hooks automation** — wire `PreToolUse`/`PostToolUse`/`Stop` lifecycle scripts via `.claude/settings.json`.
- **Context engineering** — measure and manage the context-window token budget across a codebase.

## When to Use

- Authoring, structuring, or optimizing a CLAUDE.md file for any project.
- Scaffolding a new skill package or creating a Claude Code subagent.
- Configuring hooks for automated quality, security, or workflow steps.
- Auditing and reducing context-window consumption.

## Clarify First

Before scaffolding or optimizing, settle the inputs below. When one is missing or vague and would change the result, ask about it; when it wouldn't, use a sensible default and say which one you used.

- **Which task:** scaffold a new skill, optimize a CLAUDE.md, create a subagent, or analyze context budget (selects `skill_scaffolder.py` vs `claudemd_optimizer.py` vs `context_analyzer.py`).
- **Target identity:** for a new skill: its name, domain, and one-line description; for optimization: the file or project path (the inputs the scripts require).
- **Token budget:** the target ceiling (sets `--token-limit` and what counts as over-budget).

Ask about the two or three inputs that matter most for this request, not the whole list. If the user wants a result straight away, produce it and state your assumptions at the top.

## Workflow

```bash
# Score a CLAUDE.md for structure, token cost and redundancy (default budget 6000 tokens)
python scripts/claudemd_optimizer.py CLAUDE.md --token-limit 4000

# Estimate how much of the context window a project's files would take, by category
python scripts/context_analyzer.py . --max-depth 4 --context-window 200000

# Scaffold a skill package into an existing parent directory
python scripts/skill_scaffolder.py my-skill -d engineering -o /tmp --description "Scores API specs for breaking changes"
```

All three accept `--json`. Full flags and output fields: [references/tool-reference.md](references/tool-reference.md).

- `claudemd_optimizer.py` reports a 0–100 score, the token estimate against `--token-limit`, duplicated or vague sections, and concrete cuts.
- `context_analyzer.py` defaults to a 200K window as a conservative floor. Pass the real window of the model you run, or the percentages will overstate the pressure.
- `skill_scaffolder.py` creates `<-o DIR>/<skill-name>/` with `SKILL.md`, `scripts/`, `references/` and `assets/`. `-o` (`--output`) is the parent directory, which must already exist; it defaults to the current directory, so pass `-o` to keep the scaffold out of the repo you are standing in. If the description has no "Use when" clause it appends a placeholder so you fill in the triggers before shipping.

**Exit codes (all three):** `0` report or scaffold written; `2` missing file or path, output directory that does not exist, or a skill folder that already exists. They are advisory, not gates: an over-budget CLAUDE.md still exits 0.

**Done when:** the CLAUDE.md fits its budget and every line is something the model could not infer from the code; a new skill's description says what it does and when to use it in under 240 characters; a hook has been triggered once on purpose and blocked or passed as intended.

## Anti-Patterns

### CLAUDE.md as a wiki
**Mistake:** Pasting architecture essays, full style guides and onboarding notes into CLAUDE.md.
**Why it happens:** It is the one file the agent always reads, so everything lands there.
**Instead:** Keep commands, conventions and traps the code does not reveal; link to longer docs and let the agent read them when needed. Every line costs tokens on every turn.

### Hooks that fail open
**Mistake:** A PreToolUse guard that exits 1 on a violation and assumes the tool call was blocked.
**Why it happens:** Exit 1 means "error" in most CLIs.
**Instead:** A PreToolUse hook blocks only on exit 2 (stderr goes back to the model). Test the hook against a real violating command before relying on it. See [references/hooks-cookbook.md](references/hooks-cookbook.md).

### Subagents with every tool
**Mistake:** A review subagent with no `tools` allowlist, so it can edit files and run shell commands.
**Why it happens:** Omitting `tools` is the shortest working file.
**Instead:** Give each subagent the smallest tool list its job needs; a reviewer gets read and search tools only.

## Files

- `scripts/claudemd_optimizer.py`, `scripts/context_analyzer.py`, `scripts/skill_scaffolder.py` — the three CLIs above.
- `assets/skill-template.md`, `assets/agent-template.md` — starting files for a skill and a subagent.
- `references/` — playbooks, quick reference, tool reference, skill authoring, subagent patterns, hooks cookbook.

## References

Load the reference that matches the task — keep this file lean and pull detail on demand:

- **[references/workflows.md](references/workflows.md)** — the five numbered playbooks: optimize a CLAUDE.md, author a skill, create a subagent, configure hooks, and manage the context budget. Read when executing any of those tasks step-by-step.
- **[references/quick-reference.md](references/quick-reference.md)** — slash commands, permission modes, CLAUDE.md loading order, MCP servers, the troubleshooting table, and success criteria. Read for at-a-glance lookups or when debugging configuration.
- **[references/tool-reference.md](references/tool-reference.md)** — full parameter tables and output formats for the three Python tools. Read when scripting the tools or interpreting their JSON output.
- **[references/skill-authoring-guide.md](references/skill-authoring-guide.md)** — comprehensive reference for writing effective skills, from YAML frontmatter to structure. Read when authoring a skill in depth.
- **[references/subagent-patterns.md](references/subagent-patterns.md)** — guide to creating and using subagents for parallel work and scoped tasks. Read when designing a subagent.
- **[references/hooks-cookbook.md](references/hooks-cookbook.md)** — practical hook recipes for code quality, security enforcement, and workflow automation. Read when building hooks.

**Templates:** [assets/skill-template.md](assets/skill-template.md), [assets/agent-template.md](assets/agent-template.md)

## Scope & Limitations

**This skill covers:**
- Authoring, structuring, and optimizing CLAUDE.md files for any project
- Scaffolding new skill packages with correct directory layout and frontmatter
- Creating and configuring Claude Code subagents with scoped tool access
- Analyzing and managing context window token budgets across a codebase

**This skill does NOT cover:**
- Writing application source code or implementing business logic (see [senior-fullstack](../senior-fullstack/SKILL.md), [senior-backend](../senior-backend/SKILL.md))
- MCP server development or custom transport protocols (see [mcp-server-builder](../../engineering/mcp-server-builder/SKILL.md))
- Advanced prompt engineering techniques for LLM applications (see [senior-prompt-engineer](../senior-prompt-engineer/SKILL.md))
- CI/CD pipeline configuration or deployment automation (see [senior-devops](../senior-devops/SKILL.md), [ci-cd-pipeline-builder](../../engineering/ci-cd-pipeline-builder/SKILL.md))

## See Also

- [context-engine](../context-engine/SKILL.md) — compression and prioritisation once you know the budget.
- [doc-drift-detector](../doc-drift-detector/SKILL.md) — find where CLAUDE.md no longer matches the code.
- [code-reviewer](../code-reviewer/SKILL.md) — review logic for a code-review subagent.
- [senior-prompt-engineer](../senior-prompt-engineer/SKILL.md) — wording for skill descriptions and agent prompts.

---

## What I Need You to Do

First, detect which platform I'm using (Claude.ai, ChatGPT, etc.) and follow the matching instructions below.

### If I'm on Claude.ai:

Walk me through these exact steps:

1. **Create the Project:** Tell me to go to **claude.ai > Projects > Create project** and name it **"Claude Code Mastery"**

2. **Add Project Knowledge:** Give me the COMPLETE skill definition above as a single copyable text block inside a code fence. Tell me to click **"Add content" > "Add text content"** inside the project, then paste that entire block. Do NOT say "paste from above" -- give me the actual text to copy right there.

3. **Set Custom Instructions:** Tell me to open project settings and paste this exact instruction:
   "You are an expert Claude Code Mastery in the Engineering domain. Use the project knowledge as your expertise. Follow the workflows, frameworks, and templates defined there. Always provide specific, actionable output."

4. **Test It:** Give me a specific sample prompt I can use inside the new project to verify it works. Pick a real task from the skill's workflows.

### If I'm on ChatGPT:

Walk me through these exact steps:

1. **Create a Custom GPT:** Tell me to go to **chatgpt.com > Explore GPTs > Create**
2. **Configure it:**
   - Name: **"Claude Code Mastery"**
   - Description: "Optimizes CLAUDE.md files, scaffolds skills and subagents, wires hooks and measures context budget for Claude Code. Use when writing or trimming a CLAUDE.md, creating a skill, subagent or hook, or auditing token usage."
   - Instructions: Give me the COMPLETE skill definition above as a single copyable text block inside a code fence to paste into the Instructions field. Do NOT say "paste from above."
3. **Test It:** Give me a sample prompt to verify it works.

### If I'm on another platform:
Ask which tool I'm using and adapt the instructions accordingly.

## Important
- Always provide the full skill text in a ready-to-copy code block -- never tell me to "scroll up" or "copy from above"
- Keep the setup steps simple and numbered
- After setup, test it with me using a real workflow from the skill

Source: https://github.com/borghei/Claude-Skills/tree/main/engineering/claude-code-mastery/SKILL.md