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 slbug/claude-ruby-grape-rails --skill learngit clone --depth 1 https://github.com/slbug/claude-ruby-grape-railsWrote 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/slbug/claude-ruby-grape-rails/learn)<a href="https://agentmods.dev/skills/slbug/claude-ruby-grape-rails/learn"><img src="https://agentmods.dev/badge/skills/slbug/claude-ruby-grape-rails/learn/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/slbug/claude-ruby-grape-rails/learn"><img src="https://agentmods.dev/badge/skills/slbug/claude-ruby-grape-rails/learn.svg" alt="Reviewed on agentmods" width="80" height="20"></a>- NVIDIA SkillSpector warn
SkillSpector: 1 finding, up to high
These are SkillSpector’s own severities. On a checked sample its high-severity flags on skills were ~96% false positives — a documented command, a public API, a “never do X” rule — so we show them as a caution to read, not a verdict. Why →
- high Agent Snooping · line 44 Skill reads from agent configuration directories (.claude/, .codex/, .gemini/). These directories may contain API keys, personal settings, and other credentials that the skill has no legitimate need to access.Fix: Remove all code or instructions that access agent configuration directories (.claude/, .codex/, .gemini/). If configuration values are needed, pass them explicitly as parameters or environment variabl
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 | $0.01024 |
| Opus 5.5 | $0.00016 | $0.00410 |
| Sonnet 5.5 | $0.00008 | $0.00205 |
| Haiku 4.5 | $0.00004 | $0.00102 |
Grade A, and why
rb:learn 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.
How it starts
The opening of the file, as written. The whole thing — 125 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Learn From the Fix
After fixing a bug or receiving a correction, capture the lesson to prevent future mistakes.
Usage
/rb:learn Fixed N+1 query in user listing - was missing includes
/rb:learn String vs symbol key mismatch in params handling
/rb:learn Turbo Frame needs data-turbo-frame attribute in tests
Workflow
Step 1: Identify the Root Cause
Look at recent conversation context or the file/diff the user points at. Classify the mistake:
- Knowledge gap: didn't know the correct API or pattern
- Wrong assumption: assumed behavior that doesn't match reality
- Tooling gap: lacked a check that would have caught this
- Process failure: skipped a step or checked the wrong thing
Extract the root cause, not the symptom. "Missing includes on
association" not "query was slow."
Step 2: Check for Duplicates
Before writing anything, check all existing knowledge stores:
- Read
${CLAUDE_SKILL_DIR}/references/common-mistakes.md(shipped plugin reference — READ-ONLY, never edit) - Grep project
CLAUDE.mdfor the pattern keyword - Grep
.claude/solutions/for similar fixes - Check auto-memory for similar lessons
If already documented, tell the user and stop. Do not duplicate.
Step 3: Decide Destination
CRITICAL: NEVER edit plugin files. Files under
~/.claude/plugins/ are cached and get overwritten on updates.
Always write to project or memory locations.
| Scope | Destination | When to use |
|---|---|---|
| This project only | Project CLAUDE.md |
Convention or rule for this codebase |
| Cross-project | Auto-memory | General Ruby/Rails lesson that applies everywhere |
| Complex fix | .claude/solutions/ via /rb:compound |
Multi-step debugging story |
| Safety-critical | Iron Law suggestion | Suggest to user, never auto-add |
Auto-memory requires consent. Before writing to
~/.claude/projects/{hash}/memory/, ask the user: "This lesson applies
beyond this project. Save to auto-memory for future sessions?"
What ships with it
2 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.
- 1mo ago First seen · 125 lines · 41 tokens per session scan A 82ae947ec1f1
rb:learn is a skill published in the GitHub repository slbug/claude-ruby-grape-rails (7 stars, last pushed 16d ago), licensed MIT. It adds 41 tokens to every session and 1,024 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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