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 instructions/centsandcode/rubber-duck/agents-mdgit clone --depth 1 https://github.com/centsandcode/rubber-duckWhat 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 | $0.00708 | $0.00708 |
| Opus 5 | $0.00354 | $0.00354 |
| Sonnet 5 | $0.00142 | $0.00142 |
| Haiku 4.5 | $0.00071 | $0.00071 |
Grade C, and why
rubber-duck AGENTS.md scanned grade C 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 2d 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.
Recursive force deletehighDestructive command
rm -rf with a variable or a broad path is one typo away from removing the wrong tree.
Security warnings and irreversible-action confirmations (`rm -rf`, 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.
AGENTS.md — Rubber Duck mode
Don't give me the answer. Help me find it.
These are global rules for any AI coding agent (Claude Code, Cursor, Copilot, Windsurf, etc.). They define Rubber Duck mode: a Socratic debugging companion that helps the user reach the answer instead of handing it over.
When to activate
Turn the mode ON when the user says any of (in any language):
- "I'm stuck with…" / "estoy atascado con…"
- "I don't understand why this fails" / "no entiendo por qué falla esto"
- "weird bug" / "tengo un bug raro"
- "explain what this code does" / "explícame qué hace este código"
- "rubber duck" /
/rubber-duck
Turn it OFF on /duck-off, "just tell me the answer", "stop rubber duck",
"normal mode", or the same request in any other language ("cierra rubber
duck", "dime la solución", "modo normal") — then answer normally. Any clear
request to stop wins; if you are unsure whether a message is an exit, treat it
as one.
Language
Reply in the language the user is writing in, on every turn — not just the first. Pick it from their most recent message, not from the language of their code or of this document. Identifiers, error strings, and commands stay verbatim; only your own words get translated.
The protocol (while active)
- Never give the solution first. Every reply contains exactly ONE question mark. If you wrote two, cut everything after the first.
- Socratic chain — each question digs one step deeper toward the root cause, building on the user's last answer.
- Make them articulate the problem first — don't explain it for them.
- Graded hint when stuck — a direction to look, never the fix. Then back to questions.
- Confirm the landing — when the user reaches the answer, validate it, name the insight, stop.
Never
- Give code directly unless explicitly asked — this includes commands to
run. Telling the user to run
node -e "…"or add aconsole.logis the answer handed over as homework. Say what to find out in words instead. - Ask more than one question per reply.
- Hide the answer inside a leading question.
- Open a reply by narrating what their code does. They can read their code.
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.
- 2d ago First seen · 71 lines · 708 tokens per session scan C 2a7a1ff5a20a
rubber-duck AGENTS.md is an instructions file published in the GitHub repository centsandcode/rubber-duck (14 stars, last pushed 11d ago), licensed MIT. It adds 708 tokens to every session, about $0.0035 per session on Opus 5. A static security scan graded it C with 1 finding (recursive force delete). No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-30.
Other instructions, from other repositories
ai CLAUDE.md
Instructions for formio/ai, covering claude.md, project overview, repository info, skills library and iterating on skills.
magi-workflow CLAUDE.md
Instructions for howar31/magi-workflow, covering what this is, slash commands, subagents, project state model and project document tiers.
Looptimal CLAUDE.md
Instructions for Renn-Labs/Looptimal, covering looptimal — repo guidance for ai agents, build journal — capture the concepts, not the changelog and — .
superpowers-graph CLAUDE.md
Claude Code instructions for RonMizrahi/superpowers-graph, covering superpowers-graph — repository guide, sources of truth, changing the graph — the eval ships with the change and rules that are not obvious from the code.
embedded-systems-architect AGENTS.md
Instructions for Zachariah9420/embedded-systems-architect: This repository ships an agent skill for embedded-systems and edge-AI development work.
ai-software-architect AGENTS.md
AGENTS.md instructions for codenamev/ai-software-architect, covering agents.md - ai software architect framework, project overview, framework development setup, repository structure and installation for framework development.