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 richkuo/rk-skills --skill fable-validategit clone --depth 1 https://github.com/richkuo/rk-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/richkuo/rk-skills/fable-validate)<a href="https://agentmods.dev/skills/richkuo/rk-skills/fable-validate"><img src="https://agentmods.dev/badge/skills/richkuo/rk-skills/fable-validate.svg" alt="Measured on agentmods" 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 | $0.00112 | $0.01460 |
| Opus 5 | $0.00056 | $0.00730 |
| Sonnet 5 | $0.00022 | $0.00292 |
| Haiku 4.5 | $0.00011 | $0.00146 |
Grade B, and why
fable-validate scanned grade B with 1 finding 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 4d 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.
Enumerates other installed skillsmediumAgent snooping
Other skills' SKILL.md files reveal prompts, capabilities and secrets that should be invisible to peers.
3. Any other install location — search by name, e.g. `ls ~/.claude/plugins/*/skills/validate-issue/SKILL.md` (plugin-marketplace installs live under a plugin directory, not `~/.claude/skills/`). How it starts
The opening of the file, as written. The whole thing — 71 lines — stays where its author put it; the contents beside it link to each section on GitHub.
fable-validate
Delegate issue validation to a Fable 5.1 subagent, then act on its verdict in the main agent. The subagent only validates — it never edits files or the issue; the main agent handles all follow-on actions.
Input
Same as validate-issue:
- Full URL:
https://github.com/<owner>/<repo>/issues/<N> - Short form:
#<N>or bare<N>(current repo) owner/repo#N- Nothing — default to the latest open issue in the current repo.
Steps
1. Resolve the validation procedure and the issue
Locate the validate-issue SKILL.md the subagent must follow — prefer the project-local copy over the global one, since a repo may customize the procedure:
<repo>/.claude/skills/validate-issue/SKILL.md(if it exists)~/.claude/skills/validate-issue/SKILL.md- Any other install location — search by name, e.g.
ls ~/.claude/plugins/*/skills/validate-issue/SKILL.md(plugin-marketplace installs live under a plugin directory, not~/.claude/skills/).
Record the absolute path. If none of these resolves, stop and tell the user.
If the user referenced an issue, note the number/repo but do NOT fetch or pre-validate it yourself — the subagent owns steps 0–8 of the procedure, including fetching. If no issue was referenced, the subagent resolves the latest open issue itself per the procedure.
2. Dispatch the Fable 5.1 validation subagent
Do not validate the issue yourself first — the subagent owns the validation. Load the fable-dispatch skill before dispatching: it owns the dispatch path and the dispatch-hygiene rules in its section 7 (read-only prompt, snapshot/diff, retry once then report). Dispatch per its ladder; on the Agent-tool path, call the Agent tool with:
subagent_type:Plan(read-only: no Edit/Write, keeps validation side-effect-free)model:fable(the whole point — the validation must come from Fable 5.1)run_in_background:false— everything downstream depends on the verdictdescription:Validate issue #<N>(orValidate latest issue)prompt: hand it everything needed to validate independently:- The issue reference exactly as the user gave it (or "no issue referenced — resolve the latest open issue per the procedure"), plus the working directory.
- Instruct it to read the SKILL.md at the recorded path and execute its steps 0 through 8 exactly — baseline resolution, fetch with
--comments+ PR timeline check, claim extraction, depth-rule verification withfile:linecitations, 5a/5b/5c proposal checks, complexity score, scope disposition, and the step-8 verdict format. It must read every mandatory reference file those steps name. - It must STOP at step 8: no step 9/10/11 actions, no
gh issue edit, no comments posted, no file edits — state the read-only rule explicitly in the prompt perfable-dispatchsection 7. - Return the complete step-8 verdict verbatim as its final message, plus one line stating which baseline (branch/commit) claims were traced against.
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.
- 4d ago Changed · +4 tokens per session e34e5094f2dc
- 8d ago First seen · 71 lines · 108 tokens per session scan B 2cb72a0ffa71
fable-validate is a skill published in the GitHub repository richkuo/rk-skills (49 stars, last pushed today), licensed MIT. It adds 112 tokens to every session and 1,460 once invoked, about $0.0006 per session on Opus 5. A static security scan graded it B with 1 finding (enumerates other installed skills). No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-30.
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