Writing Rules

What it does

When your agent uses it

• Adding safety guardrails
• Preventing specific commands

Example prompts

• “Use the writing-rules skill to create behavioral rules in markdown to block dangerous commands or restrict AI behavior”
• “/writing-rules”

Requirements

• Python 3
• A credential in API_KEY

Workflow steps

6 steps, taken from the first numbered list in SKILL.md.

1. 1Start with simple patterns
2. 2Test regex thoroughly
3. 3Use clear, helpful messages
4. 4Prefer warnings over blocks initially
5. 5Name rules descriptively
6. 6Document intent in messages

What it can do on your machine

Read from SKILL.md and the folder at commit 9f3eb00. It shows what the files ask for, not the result of running them.

• Tool permissions

  Pre-approves nothing: there is no allowed-tools line, so your agent's usual permission prompts apply.

  From allowed-tools in the SKILL.md frontmatter.

• Runs code

  Shell commands in SKILL.md call:

  • python3

  From the folder's file list and the shell code blocks in SKILL.md.

• Network

  No URLs in SKILL.md.

  From URLs in SKILL.md, links to its own repository left out.

• Credentials

  Names these keys or tokens, usually read from environment variables:

  • API_KEY

  From names ending in _API_KEY, _TOKEN, _SECRET, _KEY or _PASSWORD in SKILL.md.

Context cost

Writing Rules loads about 1.4k tokens when it runs. Until then it costs about 43 tokens; SKILL.md has 427 words of instructions outside code blocks.

Always · name and description, kept in context so the agent knows when to use it

~43

When it runs · the whole SKILL.md, loaded when a task matches

~1.4k

Estimates: characters ÷ 4, the usual rule of thumb; real counts depend on the model's tokenizer. Scripts and assets cost tokens only if the agent reads them.

Safety

• NoteMentions a .env fileSKILL.md:104

  🔐 **API key in .env file!**

Automated static check — not a guarantee. Review scripts before installing. It scans the text of SKILL.md for risky patterns (piping downloads into a shell, reading credential files, hidden Unicode, destructive commands); files beside SKILL.md are not scanned.

SKILL.md

The full file from athola/claude-night-market at commit 9f3eb00, republished under its MIT licence (© athola). 427 words, ~1,387 tokens.

name

writing-rules

description

Creates behavioral rules in markdown to block dangerous commands or restrict AI behavior. Use when adding safety guardrails or preventing specific commands.

alwaysApply

false

category

hook-development

tags

hookify, rules, patterns, validation, safety

estimated_tokens

2500

complexity

beginner

model_hint

fast

provides.patterns

rule-writing, pattern-matching, condition-building

provides.infrastructure

rule-validation

usage_patterns

creating-rules, pattern-matching, behavioral-enforcement

---
name: dangerous-rm
enabled: true
event: bash
pattern: rm\s+-rf
action: block
---

🛑 **Dangerous rm command detected!**

This command could delete important files.

---
name: warn-env-edits
enabled: true
event: file
action: warn
conditions:
  - field: file_path
    operator: regex_match
    pattern: \.env$
  - field: new_text
    operator: contains
    pattern: API_KEY
---

🔐 **API key in .env file!**
Ensure file is in .gitignore.

rm\s+-rf          → rm -rf
console\.log\(    → console.log(
chmod\s+777       → chmod 777

python3 -c "import re; print(re.search(r'pattern', 'text'))"

---
name: block-destructive
enabled: true
event: bash
pattern: rm\s+-rf|dd\s+if=|mkfs
action: block
---

🛑 **Destructive operation blocked!**
Can cause data loss.

---
name: warn-debug
enabled: true
event: file
pattern: console\.log\(|debugger;
action: warn
---

🐛 **Debug code detected!**
Remove before committing.

---
name: require-tests
enabled: true
event: stop
action: warn
conditions:
  - field: transcript
    operator: not_contains
    pattern: pytest|npm test
---

⚠️ **Tests not run!**
Please verify changes.

---
name: protect-prod
enabled: true
event: file
action: block
conditions:
  - field: file_path
    operator: regex_match
    pattern: /production/|\.prod\.
---

🚨 **Production file!**
Requires review.

rm .claude/hookify.my-rule.local.md

/hookify:list

© athola, MIT. Rendered from Markdown: HTML in the file is shown as text, images as links, and headings moved down two levels. Raw file

Files

Just SKILL.md in plugins/hookify/skills/writing-rules of athola/claude-night-market.

Open the folder on GitHubat commit 9f3eb00