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.
npx agentmods add skills/anthropics/claude-code/hook-developmentnpx skills add anthropics/claude-code --skill hook-developmentgit clone --depth 1 https://github.com/anthropics/claude-codeWhat 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.
| Model | Per session | Once invoked |
|---|---|---|
| Fable 5 | $0.00117 | $0.03985 |
| Opus 5 | $0.00059 | $0.01992 |
| Sonnet 5 | $0.00023 | $0.00797 |
| Haiku 4.5 | $0.00012 | $0.00398 |
Grade A, and why
Hook Development 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.
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.
The source is not reproduced here
No licence file
A repository with no LICENSE is all rights reserved by default, so the body is not copied here. The metadata, the measurements and the link are.
What ships with it
10 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.
- examples/load-context.sh 1.7 KB runs code
- examples/validate-bash.sh 1.3 KB runs code
- examples/validate-write.sh 1.2 KB runs code
- references/advanced.md 9.9 KB
- references/migration.md 8.1 KB
- references/patterns.md 7.0 KB
- scripts/hook-linter.sh 4.1 KB runs code
- scripts/README.md 3.6 KB
- scripts/test-hook.sh 5.2 KB runs code
- scripts/validate-hook-schema.sh 5.0 KB runs code
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.
- 2d ago First seen · 713 lines · 117 tokens per session scan A d14528f389ca
Hook Development is a skill published in the GitHub repository anthropics/claude-code (143,632 stars, last pushed today), with no licence file. It adds 117 tokens to every session and 3,985 once invoked, about $0.0006 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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