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 skills add oaustegard/claude-skills --skill crafting-instructionsgit clone --depth 1 https://github.com/oaustegard/claude-skillsWrote 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/oaustegard/claude-skills/crafting-instructions)<a href="https://agentmods.dev/skills/oaustegard/claude-skills/crafting-instructions"><img src="https://agentmods.dev/badge/skills/oaustegard/claude-skills/crafting-instructions/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/oaustegard/claude-skills/crafting-instructions"><img src="https://agentmods.dev/badge/skills/oaustegard/claude-skills/crafting-instructions.svg" alt="Reviewed on agentmods" width="80" height="20"></a>- NVIDIA SkillSpector pass
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 | $0.00128 | $0.02187 |
| Opus 5 | $0.00064 | $0.01094 |
| Sonnet 5 | $0.00026 | $0.00437 |
| Haiku 4.5 | $0.00013 | $0.00219 |
Grade A, and why
crafting-instructions 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 yesterday.
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.
How it starts
The opening of the file, as written. The whole thing — 276 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Crafting Instructions for Claude
Choose the format for instructions on Claude.ai — Project instructions, Skills, or standalone prompts — and structure them for the format chosen.
Overlap notice. The Core Optimization Principles below also appear in
writing-instructions, which carries them in more depth. This skill owns the
format decision; writing-instructions owns how to write well inside a
format. The two descriptions are close enough that a request can land on
either — route by which of those two questions is being asked.
Decision Framework: Which Format to Use?
Ask these questions to determine the right format:
Use PROJECT INSTRUCTIONS when:
- Context needs to persist for ALL conversations in a workspace
- Multiple team members collaborate with shared knowledge
- Background knowledge required for specific initiative
- Custom behavior scoped to one project only
Signals: "for this project", "all conversations about X", "team workspace", "project-specific"
Use SKILL when:
- Capability needed across MULTIPLE contexts/projects
- Procedural knowledge that applies broadly
- Instructions should activate automatically when relevant
- Want portable expertise that loads on-demand
Signals: "every time I", "whenever", "reusable", "across projects", "teach Claude how to"
Use STANDALONE PROMPT when:
- One-off request with immediate context
- Ad-hoc instructions for single use
- Conversational refinement
- No need for persistence
Signals: "for this task", "right now", "just this once", "can you"
Combined Approaches:
Project + Skill:
- Project: Persistent context (market data, product specs)
- Skill: Reusable methods (analysis framework, report templates)
- Use when: Need both workspace context AND portable capabilities
Skill + Prompt:
- Skill: General expertise (code review standards)
- Prompt: Specific context ("review this PR for security")
- Use when: Foundational capability + immediate direction
Core Optimization Principles
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.
- yesterday Changed · -25 lines e11110cb7cc0
- 11d ago First seen · 301 lines · 128 tokens per session scan A dbfa64530927
crafting-instructions is a skill published in the GitHub repository oaustegard/claude-skills (148 stars, last pushed yesterday), licensed MIT. It adds 128 tokens to every session and 2,187 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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