---
name: functional-design
description: Detailed guide and template for creating a functional design document. Use only when creating a functional design document.
---

# Functional Design Document Creation Skill

This skill is a detailed guide for creating high-quality functional design documents.

## Prerequisites

Before starting to create a functional design document, confirm the following:

### docs/product-requirements.md has been created

**Required**: The PRD must exist at the following location:

**File path**: `docs/product-requirements.md`

The functional design document details how to technically realize the requirements defined in the PRD.

## Priority of Existing Documents

**Important**: If an existing functional design document is present at `docs/functional-design.md`,
follow the priority order below:

1. **Existing functional design document (`docs/functional-design.md`)** - Highest priority
   - Contains project-specific design
   - Takes precedence over this skill's guide

2. **This skill's guide** - Reference material
   - Generic templates and examples
   - Use when no existing design document exists, or as a supplement

**When creating new**: Refer to this skill's template and guide
**When updating**: Update while maintaining the structure and content of the existing design document

## Output Destination

Save the created functional design document to the following location:

```
docs/functional-design.md
```

## Template Reference

When creating a functional design document, use the following template: ./template.md

## Detailed Guide

For a more detailed creation guide, refer to the following file: ./guide.md