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 sprngr/rubber-duck --skill duck-teachgit clone --depth 1 https://github.com/sprngr/rubber-duckWrote 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/sprngr/rubber-duck/duck-teach)<a href="https://agentmods.dev/skills/sprngr/rubber-duck/duck-teach"><img src="https://agentmods.dev/badge/skills/sprngr/rubber-duck/duck-teach/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/sprngr/rubber-duck/duck-teach"><img src="https://agentmods.dev/badge/skills/sprngr/rubber-duck/duck-teach.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 | $0.00045 | $0.01003 |
| Opus 5 | $0.00023 | $0.00502 |
| Sonnet 5 | $0.00009 | $0.00201 |
| Haiku 4.5 | $0.00005 | $0.00100 |
Grade A, and why
duck-teach 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 11d 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 — 115 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Tutorial generator 🦆. Structured knowledge transfer. Keep language terse and practical.
Purpose
Teach concepts with structured, minimal examples aligned to workspace patterns.
Philosophy Guardrails (skill-local)
Inherit shared guardrails from references/GUARDRAILS.md.
Skill-specific delta:
- Teach options and pitfalls; learner/developer chooses implementation path.
Activation
Use for "explain this", "what does this do", "teach me", "show me", or "walk me through" requests.
Method
1. Clarify target (if ambiguous)
-
ask 1-3 targeted clarifying questions when context is incomplete
-
state assumptions explicitly when evidence is missing
-
Preserve core safeguards in any example or recommendation:
-
If a change would weaken trust-boundary validation, security controls, data-loss prevention, accessibility requirements, or explicit user requirements, refuse it and offer only a safe alternative preserving the constraint.
Ambiguous target rule (hard):
- If user says "teach/show/walk through this" without a clear target concept/file/snippet, ask for target + desired depth first
- Do not invent or default to a topic
- Stop after clarification request until user answers
Required clarification prompt shape (when ambiguous):
- Ask for target artifact (
concept | file path | function | snippet | command) and desired depth (show me|teach me|walk me through)
2. Search codebase (if project-specific)
- Topic is project-specific -> search codebase first for real usage patterns
- Generic concept -> skip search
3. Select depth and structure
Depth scaling:
| Trigger | Output | Length target |
|---|---|---|
| "explain this" / "what does this do" | Fast 4-block explanation (What/Why/Watch out/Next question) | 8-12 lines (quick: 4-6 lines) |
| "show me X" | Compact 5-block tutorial (one-line What/Why + short Example/Pitfalls/See also) | 90-140 words |
| "teach me X" | Full 5-section tutorial | 170-260 words |
| "walk me through X" | Step-by-step numbered | 5-8 steps |
What ships with it
1 file 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.
- 11d ago First seen · 115 lines · 45 tokens per session scan A de4d589516e6
duck-teach is a skill published in the GitHub repository sprngr/rubber-duck (8 stars, last pushed yesterday), licensed MIT. It adds 45 tokens to every session and 1,003 once invoked, about $0.0002 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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