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 Casper-Studios/casper-marketplace --skill agent-skills-best-practicesgit clone --depth 1 https://github.com/Casper-Studios/casper-marketplaceWrote 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/casper-studios/casper-marketplace/agent-skills-best-practices)<a href="https://agentmods.dev/skills/casper-studios/casper-marketplace/agent-skills-best-practices"><img src="https://agentmods.dev/badge/skills/casper-studios/casper-marketplace/agent-skills-best-practices/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/casper-studios/casper-marketplace/agent-skills-best-practices"><img src="https://agentmods.dev/badge/skills/casper-studios/casper-marketplace/agent-skills-best-practices.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 | $0.00041 | $0.00497 |
| Opus 5.5 | $0.00016 | $0.00199 |
| Sonnet 5.5 | $0.00008 | $0.00099 |
| Haiku 4.5 | $0.00004 | $0.00050 |
Grade A, and why
agent-skills-best-practices 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 2mo 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.
What it actually says
Agent Skills Best Practices
Use skills for decisions, procedures, and knowledge that change how the agent works. Do not repeat documentation it can look up.
Keep essential guidance in SKILL.md. Put conditional detail in references and explain when to read each.
Show, don't tell: pair contrasting examples with a short explanation.
References
- Make the skill easy to find and invoke.
- Keep each skill focused.
- Use scripts for deterministic work and models for judgment. Prefer existing tools and standard libraries. Declare required third-party Python dependencies with PEP 723 and lock them with
uv. - Make guidance usable outside its source project.
- Keep resources portable and in the skill that owns them.
What ships with it
14 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.
- agents/openai.yaml 145 B
- LICENSE.txt 16 KB
- references/agnostic-references.md 560 B
- references/asset-distribution.md 795 B
- references/context-and-disclosure.md 1.4 KB
- references/directory-structure.md 926 B
- references/examples.md 1.2 KB
- references/executable-scripts.md 1.5 KB
- references/library-sources.md 835 B
- references/prose-and-formatting.md 841 B
- references/reference-routing.md 2.2 KB
- references/skill-naming.md 820 B
- references/skill-scope.md 574 B
- references/trigger-descriptions.md 979 B
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.
- 2mo ago Changed · +7 lines · -32 tokens per session c19b8d6a6e39
- 2mo ago First seen · 30 lines · 73 tokens per session scan A 144517df1e1b
agent-skills-best-practices is a skill published in the GitHub repository Casper-Studios/casper-marketplace (14 stars, last pushed yesterday), licensed MPL-2.0. It adds 41 tokens to every session and 497 once invoked, about $0.0002 per session on Opus 5.5. 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.
agent-skills-best-practices compared with skills from other repositories
| Mod | Type | Stars | Last push | Licence | Scan | Tokens | Works with |
|---|---|---|---|---|---|---|---|
| agent-skills-best-practicesCasper-Studios/casper-marketplace | Skill | 14 | yesterday | MPL-2.0 | A | 41 | Codex |
| imagegenopenai/codex | Skill | 135k | today | Apache-2.0 | A | 113 | Codex |
| playwright-climicrosoft/playwright | Skill | 100k | yesterday | Apache-2.0 | A | 19 | Claude Code |
| browser-automationopenclaw/openclaw | Skill | 394k | today | MIT | A | 36 | Claude Code |
| local-ai-agentsmicrosoft/ai-agents-for-beginners | Skill | 80k | 7d ago | MIT | A | 200 | Claude Code, Codex |
| next-cache-components-adoptionvercel/next.js | Skill | 144k | today | MIT | A | 95 | Claude Code |
| chat-pet-sprite-creationmicrosoft/vscode | Skill | 195k | today | MIT | A | 53 | Claude Code, Codex |