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 ychampion/cskill-agents --skill skip-skill-listing-without-skill-toolgit clone --depth 1 https://github.com/ychampion/cskill-agentsWrote 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/ychampion/cskill-agents/skip-skill-listing-without-skill-tool)<a href="https://agentmods.dev/skills/ychampion/cskill-agents/skip-skill-listing-without-skill-tool"><img src="https://agentmods.dev/badge/skills/ychampion/cskill-agents/skip-skill-listing-without-skill-tool/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/ychampion/cskill-agents/skip-skill-listing-without-skill-tool"><img src="https://agentmods.dev/badge/skills/ychampion/cskill-agents/skip-skill-listing-without-skill-tool.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 | $0.00390 |
| Opus 5.5 | $0.00016 | $0.00156 |
| Sonnet 5.5 | $0.00008 | $0.00078 |
| Haiku 4.5 | $0.00004 | $0.00039 |
Grade A, and why
skip-skill-listing-without-skill-tool 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.
What it actually says
SKILL: Skip Skill Listing Without Skill Tool
Domain: command-surfaces
Trigger: Apply when an attachment or context injector is about to advertise capabilities to an agent that may not have the tool needed to use them.
Source Pattern: Distilled from reviewed command-surface and listing-control patterns.
Core Method
Before generating capability-discovery context, verify that the receiving agent actually exposes the execution surface for it. If the agent lacks the Skill tool, return no skill-listing attachment at all rather than spending tokens on a catalog it cannot invoke. This keeps the prompt focused on actionable affordances and avoids confusing agents with instructions they have no mechanism to execute.
Key Rules
- Check tool availability before doing any skill-listing work, including command collection or formatting.
- Treat missing execution surfaces as a hard stop, not as a degraded listing mode.
- Keep the guard close to the listing entrypoint so later refactors cannot accidentally compute listings for unsupported agents.
- Prefer actionable context over informative-but-unusable context; if the agent cannot call the tool, omit the attachment.
Example Application
If a background helper agent is configured only with file and shell tools, skip injecting a skill catalog even if the parent session supports skills. The helper sees only the tools it can actually use, while the main agent continues receiving skill-listing updates normally.
Anti-Patterns (What NOT to do)
- Do not send a skill listing just because the overall application supports skills; the specific consumer must expose the
Skilltool. - Do not compute and then discard the listing after expensive formatting work; guard before the heavy path starts.
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 · 28 lines · 41 tokens per session scan A cd40d007e46d
skip-skill-listing-without-skill-tool is a skill published in the GitHub repository ychampion/cskill-agents (36 stars, last pushed 6mo ago), licensed MIT. It adds 41 tokens to every session and 390 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 2026-09-03.
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