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 agentmods add skills/theshadow27/mcp-cli/rule-authornpx skills add theshadow27/mcp-cli --skill rule-authorgit clone --depth 1 https://github.com/theshadow27/mcp-cliWrote 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/theshadow27/mcp-cli/rule-author)<a href="https://agentmods.dev/skills/theshadow27/mcp-cli/rule-author"><img src="https://agentmods.dev/badge/skills/theshadow27/mcp-cli/rule-author.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 | $0.00160 | $0.01192 |
| Opus 5 | $0.00080 | $0.00596 |
| Sonnet 5 | $0.00032 | $0.00238 |
| Haiku 4.5 | $0.00016 | $0.00119 |
Grade A, and why
rule-author 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 5d 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.
How it starts
The opening of the file, as written. The whole thing — 43 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Rule Author
The rule lifecycle is harvest → init → add. This skill routes on its argument:
/rule-author harvest— mine merged PRs for recurring author mistakes that could become rules. Seereferences/harvest.md./rule-author init— bootstrap the rule engine into a repo. Seereferences/rule-engine.md./rule-author add <rule>— author a new rule. Seereferences/new-rule.md.- no argument — this overview + the "is this a good rule?" triage below.
Why rules exist
A rule mechanizes a recurring mistake so review rounds and CI minutes are spent on judgment, not on catching the same avoidable bug again and again. Rules are part of the project's definition of done: the doing-it-wrong sweep runs inside am-i-done, which is the single gate executed identically at pre-commit and in CI. That's the whole value — it shifts failures left: a violation fails in seconds on the author's machine instead of surfacing minutes later in CI (or worse, never, if the gate is incomplete). And because mcp-cli is built by autonomous agents, rules are agentic guardrails: an implementer that doesn't know a convention gets caught mechanically instead of shipping the mistake into main. One rule is one scripts/rules/<id>.rule.ts file — not a new package.json script. New rules go behind the single doing-it-wrong / am-i-done entry points.
When to use this skill
- Writing a new rule from a known recurring mistake (e.g. a
/rule-author harvestfinding). - Refining a rule that's too broad (false positives) or too narrow (misses the shape).
- Judging whether a proposed invariant should be a rule at all.
- Migrating a legacy standalone
scripts/check-*.tsinto the engine. - Standing the engine up in a new repository.
References
references/harvest.md—/rule-author harvest: the survey → cluster → decide pipeline for mining merged-PR review comments. The per-agent classifier prompt lives inreferences/extract.mdand the extractor inscripts/extract-pr.ts.references/new-rule.md— how to author a.rule.ts: the API, regex-vs-AST decision, fixtures (minimal, not elaborate), writing guidance that names the cause, and the add-rule→show-red→remediate-in-the-same-PR discipline.references/rule-engine.md— a from-scratch description of the engine (every_engine/component, the entry scripts, and how the gate is wired). Use this when copying the engine to a new repo so you don't re-derive the layout each time.
What ships with it
5 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.
- 5d ago First seen · 43 lines · 160 tokens per session scan A 3e3bd81bcb36
rule-author is a skill published in the GitHub repository theshadow27/mcp-cli (2 stars, last pushed yesterday), licensed MIT. It adds 160 tokens to every session and 1,192 once invoked, about $0.0008 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 2026-08-31.
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