Explain Step By Step

Step-by-Step Explanation Skill

You explain complex things progressively, building understanding layer by layer.

Philosophy

• Progressive disclosure - Start with the big picture, then details
• Logical ordering - Present steps in the order that builds understanding
• Efficient - No filler words, no over-explanation
• Domain-agnostic - Works for code, PRs, documents, concepts, anything

Process

1. Identify What to Explain

Determine the subject:

• PR/commit changes
• Code file or function
• Architecture or system
• Document or spec
• Concept or process
• Error or behavior

2. Gather Context

For PRs/code changes:

# Get the diff
git diff main...HEAD  # or specific commits
gh pr diff    # for GitHub PRs

For code:

• Read the relevant files
• Use LSP for definitions/references if helpful

For concepts:

• Draw on your knowledge
• Research if needed (WebSearch)

3. Structure the Explanation

Always start with a 1-2 sentence summary:

This PR adds rate limiting to the API by introducing a Redis-backed
token bucket and applying it to all authenticated endpoints.

Then break into logical steps:

| Subject Type | Step Ordering | |--------------|---------------| | PR/changes | By logical dependency, not file order | | Code flow | By execution order | | Architecture | Outside-in (boundaries -> core) or inside-out | | Process | Chronological or causal | | Concept | Simple -> complex, concrete -> abstract |

4. Present Each Step

Format each step as:

## Step N: [What This Step Accomplishes]

[1-2 sentences explaining the step]

[Code snippet or relevant excerpt if applicable]

**Key insight:** [One sentence on why this matters or what to notice]

5. Connect the Steps

After all steps, optionally add:

• How the pieces fit together
• What to watch out for
• Questions the reader might have

Example: Explaining PR Changes

Input: "Explain this PR"

Output:

## Summary

This PR adds user session management with automatic timeout and refresh.

---

## Step 1: New Session Model

Adds `Session` struct with user ID, expiry, and refresh token.

```rust
pub struct Session {
    user_id: Uuid,
    expires_at: DateTime,
    refresh_token: String,
}

Key insight: Sessions are stored server-side, not in JWT claims.

---

Step 2: Session Middleware

New middleware checks session validity on each request.

async fn session_check(req: Request, next: Next) -> Response {
    let session = get_session(&req)?;
    if session.is_expired() {
        return Err(Unauthorized);
    }
    next.run(req).await
}

Key insight: Expired sessions return 401, forcing re-auth.

---

Step 3: Refresh Endpoint

Adds /auth/refresh to extend sessions without re-login.

Key insight: Refresh tokens are single-use and rotated on each refresh.

---

How It Fits Together

Request -> Middleware checks session -> If valid, proceed -> If expired, client calls refresh -> New session issued

Watch out for: The refresh token rotation means clients must store the new token after each refresh.

## Adapting to Domain

### For Code Explanation

- Follow execution flow
- Highlight state changes
- Note side effects

### For Architecture

- Start with boundaries (what goes in/out)
- Then internal components
- Then data flow between them

### For Concepts

- Start with what it is (definition)
- Then why it exists (motivation)
- Then how it works (mechanism)
- Then when to use it (application)

### For Errors/Debugging

- Start with the symptom
- Then the cause chain
- Then the fix

## Anti-Patterns

**DON'T:**
- Explain in file order (often wrong logical order)
- Include every detail (focus on what builds understanding)
- Use filler ("Let me explain...", "As you can see...")
- Assume knowledge level (calibrate to user)

**DO:**
- Start with summary
- Order by logical dependency
- Use code snippets sparingly but effectively
- End with connections/insights

## Efficiency Tips

- If user knows the domain, skip basics
- If change is trivial, say so briefly
- If step is obvious, compress it
- If something is complex, expand it

## Output Branding

Use `[explain]` prefix for multi-part explanations:

[explain] Breaking down this PR in 4 steps...

Summary

...

For simple explanations, skip the prefix.

## Source & license

This open-source skill is cataloged on AgentStack and links to its original source — we do not rehost the code.

- **Author:** [hknc](https://github.com/hknc)
- **Source:** [hknc/claude-evolve](https://github.com/hknc/claude-evolve)
- **License:** MIT

Install and usage instructions live in the source repository linked above.