design-doc

name	design-doc
description	Use when creating or organizing design documents. Provides directory structure, file naming, and content guidelines for design specs and references.
allowed-tools	Read, Write, Glob, Grep

Design Documentation Skill

This skill provides guidelines for creating and organizing design documents in this project.

When to Apply

Apply this skill when:

• Creating new design documents
• Documenting research or investigation results
• Recording architectural decisions

Output Location

IMPORTANT: All design documents MUST be stored under design-docs/ subdirectories (NOT directly under design-docs/).

design-docs/
├── specs/             # Design specifications (keep file count minimal)
│   ├── command.md     # CLI command interface design
│   ├── architecture.md # System architecture design
│   ├── notes.md       # Other notable design items
│   └── design-*.md    # Detailed supporting documents (if needed)
├── references/        # External reference materials
│   └── README.md      # Index of all references
└── user-qa/           # Items requiring user confirmation
    └── README.md      # Index of pending questions

Directory Rules

Directory	Purpose
design-docs/specs/	Design specifications (3 main files + supporting docs)
design-docs/references/	External reference materials and links
design-docs/user-qa/	Questions and items requiring user confirmation

DO NOT create markdown files directly under design-docs/.

Specs Directory Structure

Keep file count minimal. Use 3 main category files:

File	Purpose
command.md	CLI command interface: subcommands, flags, options, environment variables
architecture.md	System architecture, infrastructure, technical decisions
notes.md	Other notable items, research findings, miscellaneous design notes

Adding Content

1. Determine the appropriate category (command, architecture, or notes)
2. Add a new section to the corresponding file
3. For detailed/lengthy content, create a supporting design-*.md file and reference it

Supporting Documents

When content is too detailed for the main category files:

1. Create design-docs/specs/design-<topic>.md
2. Add a reference in the appropriate category file

User Q&A Directory

Items requiring user confirmation MUST be stored in design-docs/user-qa/.

When to Use

• Questions requiring user decision
• Ambiguous requirements needing clarification
• Design choices awaiting approval
• Implementation alternatives for user selection

File Naming

Prefix	Use Case
qa-	Questions/confirmation items
pending-	Pending decisions

References Directory

All external references MUST be stored in design-docs/references/.

Adding References

1. Add the reference entry to design-docs/references/README.md
2. For detailed reference materials, create a topic subdirectory (e.g., references/rust/)
3. Link to design-docs/references/ in design documents

Document Template

For supporting documents (design-*.md):

# Document Title

Brief description of what this document covers.

## Overview

High-level summary of the topic.

## Technical Details

Detailed technical information.

## Usage Examples

Practical examples:

\`\`\`bash
# Example commands or code
\`\`\`

## References

See `design-docs/references/README.md` for external references.

Code Content Guidelines

Design documents should prioritize readability and conceptual clarity over implementation details.

General Rule

Minimize actual code in design documents. Excessive code reduces readability and shifts focus from design concepts to implementation specifics.

When Code is Acceptable

Code may be included when it serves a clear design purpose:

Use Case	Guideline
Reference implementation	Keep concise; show only essential patterns
Implementation comparison	Show minimal examples highlighting key differences
API signatures	Include type signatures without full implementation
Configuration examples	Show structure, omit boilerplate

Best Practices

1. Prefer pseudocode or diagrams over actual code when explaining concepts
2. Extract only relevant lines rather than including entire functions/files
3. Use comments to highlight key points in code examples
4. Link to source files instead of copying large code blocks
5. Maximum code block length: aim for 10-20 lines; longer blocks should be split or summarized

Example: Good vs Verbose

Verbose (avoid):

// Full implementation with all error handling, imports, etc.
use std::sync::Arc;
use tokio::sync::Mutex;
// ... many imports
// ... 50+ lines of code

Concise (preferred):

// Key pattern: dependency injection
pub struct Service {
    repo: Arc<dyn Repository>,
}

impl Service {
    pub async fn process(&self, data: Input) -> Result<Output, Error> { /* ... */ }
}

Quick Reference

Main Category Files

File	Content
command.md	CLI interface: subcommands, flags, options, env vars, exit codes
architecture.md	System design, infrastructure, APIs, data flow
notes.md	Research results, investigations, miscellaneous notes

When to Create Supporting Files

Create design-*.md only when:

• Content exceeds reasonable section length
• Topic requires detailed technical documentation
• Document needs frequent independent reference