# Teach Back

> Teach-Back (Feynman)

- Skill: `opelpleple/teach-back` (Agent Skill)
- Install (CLI): `npx skillmds@latest add opelpleple/teach-back`
- Raw SKILL.md: https://api.skillmd.com/api/skills/opelpleple/teach-back/raw
- Safety review: pending
- Works with: Claude Code, Claude.ai, OpenAI Codex
- Category: Coding & Dev Tools
- Author: opelpleple (https://skillmd.com/u/opelpleple)
- Updated: 2026-09-17
- Page: https://skillmd.com/skills/opelpleple/teach-back

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# Teach-Back (Feynman)

Understanding is the ability to explain a thing simply; wherever plain language fails, that is exactly where understanding is missing. This skill drives a concept down to ten-year-old clarity and treats every stumble as a map to the gap.

## When to use
- The user is learning a new concept and wants to confirm they truly grasp it.
- They ask for an "explain like I'm 5" / ELI5 / simplest-terms explanation.
- They want to be tested on whether their mental model holds up.
- They're studying for an exam, interview, or want something to actually stick.
- They've read or been told something and aren't sure it landed.

## When NOT to use
- They want a fast factual lookup or a definition, not deep understanding ("what's the capital of France").
- They need a rigorous, jargon-correct technical spec (e.g. a precise API contract) — oversimplifying would mislead.
- They're an expert seeking nuance or edge cases, not foundational clarity.
- The task is to produce a polished artifact (essay, doc), not to learn.

## The method (numbered, concrete — the heart)
1. **Name the one concept.** Pin down a single, specific thing to understand. If the user gives something broad ("machine learning"), narrow to one teachable chunk ("how a model learns from one example").
2. **Pick the mode.** Either (a) *you teach it back to them* in the simplest terms, or (b) *they teach it to you* and you probe. Ask which they want; default to (a) for "explain it," (b) for "test me / do I understand."
3. **Explain at a 10-year-old level.** Short sentences. Zero jargon — and if a technical word is unavoidable, immediately define it in plain words. Use one concrete analogy from everyday life (kitchens, sports, money, traffic), not another abstraction.
4. **Hunt the seams.** As you (or they) explain, watch for the moment the words get vague, hand-wavy, or fall back on the jargon you were trying to avoid ("it just optimizes the loss"). That stall *is* the gap. Flag it out loud: "Right here is where it gets fuzzy."
5. **Drill the gap with a child's question.** Ask the dumb-on-purpose "but why?" or "what does that actually mean?" Keep asking until the explanation reaches bedrock or visibly breaks.
6. **Patch and re-simplify.** Fill the exposed gap, then restate the whole thing once more, even simpler than before. The second pass should be shorter, not longer.
7. **Close with a one-sentence summary** the user could repeat from memory, plus the single weakest spot they should review next.

## What good looks like
- A child could follow the explanation and repeat the gist.
- Every analogy maps cleanly onto the real mechanism (no analogy that quietly lies).
- Gaps are named explicitly, not glossed over to sound smooth.
- The final version is shorter and clearer than the first.
- The user leaves knowing both what they understand and the one thing they don't.

## Anti-patterns
- Hiding behind jargon to *sound* rigorous instead of proving understanding.
- A confident, fluent explanation that never tests itself — fluency is not understanding.
- Analogies that are cute but structurally wrong.
- Piling on more detail when the fix is more clarity.
- Letting the user nod along; if they never stumble, you didn't probe hard enough.

## Example (short, vivid)
User: "Help me learn how interest compounds — do I actually get it?"
Mode (b): "Teach it to me like I'm 10."
User: "You earn interest on your interest." → "Okay — but *why* does that grow faster than plain interest? Walk me through year two with $100 at 10%." User: "Year one... $110. Year two... uh, another $10?" → "Stall. That's the gap. Plain interest gives $10/yr forever. Compounding charges year two's 10% on $110, not $100 — so $11, then $12.10... the base keeps growing. Now you teach me year three." User nails it. → One-liner to keep: *"Compounding pays you on your past payouts, so the pile snowballs."* Weak spot to review: how the rate-vs-time tradeoff changes the snowball.