85dfa2ef2e
The !`command` blocks in SKILL.md go through Claude Code's Bash permission checker, which rejects $() command substitution. Simplified the git log command, replaced dynamic verify script path with a Read tool instruction, and narrowed allowed-tools to specific command patterns. Also documented the constraints in CLAUDE.md for future skill development. Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
45 lines
3.0 KiB
Markdown
45 lines
3.0 KiB
Markdown
# Custom Claude Skills
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Reusable Claude Code skills shared across all projects via symlinks into `~/.claude/skills/`.
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## Repository Structure
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```
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custom-claude-skills/
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├── CLAUDE.md # This file
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├── MEMORY.md # Learnings about skill development
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├── FUTURE.md # Future skill ideas
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├── README.md # Setup instructions and skill catalogue
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├── scripts/
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│ └── install.sh # Symlinks all skills into ~/.claude/skills/
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└── skills/
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└── reflect/
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└── SKILL.md # Milestone reflection skill
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```
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## Conventions
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- Each skill lives in `skills/<skill-name>/SKILL.md`
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- Skills should be project-agnostic where possible — use dynamic context injection (`!`command``) to adapt to the current project
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- The `scripts/install.sh` script creates symlinks from `~/.claude/skills/<name>` → this repo's `skills/<name>/`
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- After adding a new skill, run `./scripts/install.sh` to register it
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- Skills that are only useful for one project should live in that project's `.claude/skills/` instead
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## Skill Development Guidelines
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- **Inline by default** — only use `context: fork` if the skill genuinely doesn't need conversation history
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- **Pre-fetch context** with `!`command`` injection to reduce tool calls during execution
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- **Restrict tools** with `allowed-tools` to the minimum needed — this reduces permission prompts
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- **Use $ARGUMENTS** for user input, `$0`, `$1` etc. for positional args
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- Dynamic commands in `!`command`` run at skill load time, not during Claude's execution
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## `!`command`` Gotchas
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The `!`command`` syntax in SKILL.md runs shell commands at skill load time to pre-gather context. These commands go through Claude Code's Bash permission checker against the `allowed-tools` patterns. Key constraints:
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- **No `$()` command substitution** — the permission checker rejects commands containing `$()` even if the outer command matches an allowed pattern. This means you cannot nest subshells (e.g., `git log --since="$(git log ...)"` will fail).
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- **No complex shell pipelines relying on subshells** — keep `!`command`` commands simple and self-contained. If you need complex logic, have the skill instructions tell Claude to run it via tool calls instead.
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- **`allowed-tools` patterns must match the command binary** — `Bash(git *)` allows any `git` subcommand, but `Bash(cat *)`, `Bash(sed *)`, `Bash(ls *)` must be listed separately if those commands appear in `!`command`` blocks.
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- **Prefer specific tool patterns over broad ones** — `Bash(git log *)`, `Bash(git diff *)` is safer than `Bash(git *)` to avoid accidentally allowing destructive git commands (e.g., `git reset`, `git push --force`).
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- **Fallback to tool instructions for dynamic paths** — if a command needs `$ARGUMENTS` to compute a file path (e.g., `cat scripts/verify-m${N}.sh`), replace the `!`command`` with a plain-text instruction telling Claude to use the Read tool. This avoids `$()` substitution and is more reliable.
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