🔗Composition
Hook fires skill
Composition example: PostToolUse hook detects a command and queues a slash command for the next turn.
- Surfaces
- hook · skill · trigger
- Complexity
- advanced
- Trigger
- hook
- Est. tokens
- 2,000
What It Does
When Claude runs a DB migration command, a PostToolUse hook detects it and appends a slash command (e.g. /verify-migration) to the prompt queue. On Claude's next turn, the verification skill runs automatically. The hook does the detection; the skill does the verification.
When It Triggers
- ▸PostToolUse on Bash commands matching migration patterns (alembic upgrade, prisma migrate)
- ▸Fires after the migration completes — verification runs next
SKILL.md
markdown
---
name: hook-fires-skill
description: Example of a PostToolUse hook that invokes a skill after specific tool calls. Wires a Bash-run migration to auto-trigger a verification skill.
---
# Hook Fires Skill
## Flow
1. User runs a DB migration via Bash
2. PostToolUse hook detects `alembic upgrade` or `prisma migrate`
3. Hook appends `/verify-migration` to the user's prompt queue
4. Claude picks up the slash command on its next turn and runs the skill
## Install
See `settings.json` in the files section.
settings.json
json
{
"hooks": {
"PostToolUse": [
{
"matcher": "Bash",
"commandMatcher": "(alembic upgrade|prisma migrate)",
"command": "echo '/verify-migration' >> \"$CLAUDE_PROMPT_QUEUE\""
}
]
}
}
Why Two Primitives
Hooks are deterministic shell commands — fast, free of tokens, perfect for detection. Skills are Claude-powered workflows — good for verification, reasoning, and structured output. Combining them keeps detection cheap and verification smart.