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 avivsinai/skills-marketplace --skill write-skillsgit clone --depth 1 https://github.com/avivsinai/skills-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/avivsinai/skills-marketplace/write-skills)<a href="https://agentmods.dev/skills/avivsinai/skills-marketplace/write-skills"><img src="https://agentmods.dev/badge/skills/avivsinai/skills-marketplace/write-skills/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/avivsinai/skills-marketplace/write-skills"><img src="https://agentmods.dev/badge/skills/avivsinai/skills-marketplace/write-skills.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 | $0.00092 | $0.02480 |
| Opus 5.5 | $0.00037 | $0.00992 |
| Sonnet 5.5 | $0.00018 | $0.00496 |
| Haiku 4.5 | $0.00009 | $0.00248 |
Grade A, and why
write-skills 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.
This is a copy
92% identical to write-skills — 23 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 — 224 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Write Skills
A skill is not documentation. It is compressed operational memory for an agent that already knows how to code and reason. Its job is predictability — the agent taking the same process every run, not producing the same output. Put only the context that changes what the agent will do.
First Principles
-
Trigger from the description. The frontmatter
descriptionis the only part read before the skill loads. Say what the skill does and the concrete situations that should trigger it. Do not hide trigger rules in the body. -
Spend tokens like they are scarce. Assume the agent is already good at general reasoning. Keep only non-obvious workflow, domain constraints, tool choices, failure modes, and validation rules. Delete background, motivation, and generic advice.
-
Write procedures, not essays. Prefer imperative rules, decision points, and small examples. A good skill changes behavior in the next turn; it does not merely explain the topic. And match the procedure to the deliverable's shape: a catalog of techniques with "pick what fits" produces tool-picking, not a flow — if the job is a shaped interaction (an interview, a staged walk), the workflow must be that shape, with the techniques demoted to steps inside it.
-
Use progressive disclosure. Keep the main skill file short. Push long schemas, examples, provider docs, or variant-specific guidance out into linked
references/files, reached by a pointer that fires only when needed. Put repeatable fragile operations inscripts/. Put reusable output material inassets/. -
Validate by use. A skill is good when a fresh agent applies it correctly on a realistic task — run it blind, and on the weakest model that will run it; a skill that only drives correct behavior on the frontier model that authored it is too fragile to ship. After editing, read it as if you had no conversation history and remove anything that would not affect action.
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 First seen · 224 lines · 92 tokens per session scan A 8ff17e7af015
write-skills is a skill published in the GitHub repository avivsinai/skills-marketplace (2 stars, last pushed yesterday), licensed MIT. It adds 92 tokens to every session and 2,480 once invoked, about $0.0004 per session on Opus 5.5. A static security scan graded it A with 0 findings. It is 92% identical to write-skills, differing in 23 lines, and is treated as a copy.
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