Borrowing it
Nothing to install: this file belongs to dwalleck/catalyst. Take a copy, put it at the same path in your own repository, and replace the rules that are about this project with yours.
curl -O https://raw.githubusercontent.com/dwalleck/catalyst/main/.claude/skills/skill-developer/SKILL.mdgit clone --depth 1 https://github.com/dwalleck/catalystWrote this? Show the measurements
A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.
[](https://agentmods.dev/skills/dwalleck/catalyst/skill-developer)<a href="https://agentmods.dev/skills/dwalleck/catalyst/skill-developer"><img src="https://agentmods.dev/badge/skills/dwalleck/catalyst/skill-developer/github.svg" alt="Measured on agentmods" height="20"></a>Or the 80×15 button, for a site that already has a row of RSS and ATOM ones. Only the verdict fits; the numbers stay here.
<a href="https://agentmods.dev/skills/dwalleck/catalyst/skill-developer"><img src="https://agentmods.dev/badge/skills/dwalleck/catalyst/skill-developer.svg" alt="Reviewed on agentmods" width="80" height="20"></a>What 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 5.1 | $0.00097 | $0.02914 |
| Opus 5.5 | $0.00039 | $0.01166 |
| Sonnet 5.5 | $0.00019 | $0.00583 |
| Haiku 4.5 | $0.00010 | $0.00291 |
Grade A, and why
skill-developer 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 1mo 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.
This is a copy
86% identical to skill-developer — 54 lines differ, which has more behind it and is treated as the original. This page carries a canonical link to it rather than competing with it.
How it starts
The opening of the file, as written. The whole thing — 427 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Skill Developer Guide
Purpose
Comprehensive guide for creating and managing skills in Claude Code with auto-activation system, following Anthropic's official best practices including the 500-line rule and progressive disclosure pattern.
When to Use This Skill
Automatically activates when you mention:
- Creating or adding skills
- Modifying skill triggers or rules
- Understanding how skill activation works
- Debugging skill activation issues
- Working with skill-rules.json
- Hook system mechanics
- Claude Code best practices
- Progressive disclosure
- YAML frontmatter
- 500-line rule
System Overview
Two-Hook Architecture
1. UserPromptSubmit Hook (Proactive Suggestions)
- File:
.claude/hooks/skill-activation-prompt.ts - Trigger: BEFORE Claude sees user's prompt
- Purpose: Suggest relevant skills based on keywords + intent patterns
- Method: Injects formatted reminder as context (stdout → Claude's input)
- Use Cases: Topic-based skills, implicit work detection
2. Stop Hook - Error Handling Reminder (Gentle Reminders)
- File:
.claude/hooks/error-handling-reminder.ts - Trigger: AFTER Claude finishes responding
- Purpose: Gentle reminder to self-assess error handling in code written
- Method: Analyzes edited files for risky patterns, displays reminder if needed
- Use Cases: Error handling awareness without blocking friction
Philosophy Change (2025-10-27): We moved away from blocking PreToolUse for Sentry/error handling. Instead, use gentle post-response reminders that don't block workflow but maintain code quality awareness.
Configuration File
Location: .claude/skills/skill-rules.json
Defines:
- All skills and their trigger conditions
- Enforcement levels (block, suggest, warn)
- File path patterns (glob)
- Content detection patterns (regex)
- Skip conditions (session tracking, file markers, env vars)
Skill Types
1. Guardrail Skills
Purpose: Enforce critical best practices that prevent errors
What ships with it
6 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.
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.
- 1mo ago First seen · 427 lines · 97 tokens per session scan A f4b4a4cd9ae4
skill-developer is a skill published in the GitHub repository dwalleck/catalyst (11 stars, last pushed 11mo ago), licensed MIT. It adds 97 tokens to every session and 2,914 once invoked, about $0.0004 per session on Opus 5.5. A static security scan graded it A with 0 findings. It is 86% identical to skill-developer, differing in 54 lines, and is treated as a copy.
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