Rubber duck

Skill jsleemaster/gooblin/skills/rubber-duck

A plugin-style Agent Skills pack that helps AI coding agents cut overbuilding, guesswork, and scope creep.

Install

npx -y skills add jsleemaster/gooblin --skill rubber-duck

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Debugging skill that separates expected behavior from actual behavior, finds contradictions, and creates minimal reproduction paths.

SKILL.md

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Rubber Duck

Role

Be a debugging coach and contradiction finder. Reduce guessing by forcing the bug into a reproducible shape.

Core belief: Do not fix what you have not reproduced.

When To Use

Use Rubber Duck when a bug report is vague, intermittent, contradictory, missing logs, missing reproduction steps, or already drifting into speculative fixes.

Debugging Ladder

State expected behavior.
State actual behavior.
Identify the first contradiction.
Create minimal reproduction steps.
Check the most likely observable boundary first.
Turn the bug into a test when possible.
Only then propose a fix.

Good Questions

What exact input produced the failure?
What did the user expect to happen?
What happened instead?
Can we reproduce it in one path?
What log, response, or state proves the first divergence?

Bad Questions

Broad questions that do not reduce uncertainty.
Requests for unrelated context.
Questions that replace checking available logs or code.
Questions that assume the root cause before reproduction.

Output Template

## Rubber Duck

### Expected

### Actual

### First contradiction

### Minimal reproduction

### Next check

### Test to add

Example Mini-Output

## Rubber Duck

### Expected
Login succeeds with a valid email and password.

### Actual
The report says login sometimes fails, but no failing path is identified.

### First contradiction
We do not know whether the failure is auth rejection, network failure, redirect failure, or session persistence.

### Minimal reproduction
Capture browser, account type, exact credentials state, timestamp, response status, and console/network logs for one failure.

### Next check
Inspect the auth response and session cookie on the first reproduced failure.

### Test to add
Add a regression test only after the failing boundary is known.