explain

name	explain
description	Explain code in detail - what it does, how it works, and why. Use when you need to understand unfamiliar code or explain code to others.
argument-hint	[file path, file:line-range, or function name]

Explain Code

Provide a clear, thorough explanation of the specified code.

Input

The user will provide one of:

• A file path: /explain src/auth/jwt.ts
• A file path with line range: /explain src/auth/jwt.ts:45-80
• A function/class name: /explain parseToken
• Just /explain — explain the currently open or most recently discussed file

Explanation Structure

1. Overview (2-3 sentences)

What does this code do at a high level? What problem does it solve?

2. Key Components

Break down the major parts:

## Function: functionName

**Purpose:** One sentence description

**Parameters:**
- `param1` (type) — what it's for
- `param2` (type) — what it's for

**Returns:** What and when

**Side effects:** Any mutations, API calls, state changes

3. Control Flow

Explain the execution path:

1. First, it does X
2. Then checks Y
3. If Y is true, Z happens
4. Otherwise, W happens

Use a simple flowchart for complex logic:

Input -> Validate -> Transform -> Output
              |
           Error -> Log -> Return null

4. Dependencies

What does this code depend on?

• External libraries
• Internal modules
• Environment variables
• Database/API connections

5. Gotchas & Edge Cases

Things that might surprise someone:

• Non-obvious behavior
• Edge cases handled (or not handled)
• Performance considerations
• Known limitations

6. Usage Example

Show how to use this code:

// Example usage
const result = functionName(arg1, arg2);

Tone

• Assume the reader is a competent developer unfamiliar with this specific code
• Avoid jargon unless defining it
• Use "this code" not "the code" for clarity
• Be concise but complete