天完成了需求分析和開發模式選擇，今天要產出專業的 PRD（Product Requirements Document）文件。這份文件將成為未來 5 天開發的最重要的基礎，也是 AI 理解專案的關鍵上下文。

為什麼 PRD 這麼重要？

很多開發者討厭寫文件，覺得是浪費時間。但在 AI-DLC Sprint 中，PRD 是投資，不是成本：

1. 給 AI 完整上下文：越詳細的 PRD，AI 產生的程式碼越精準
2. 避免範圍蔓延：明確什麼要做、什麼不做
3. 對齊認知：確保你和 AI 的理解一致
4. 未來的資產：三個月後你還記得當初為什麼這樣設計

與 AI 協作撰寫 PRD

建立 AI Agent

---
name: Spec Driven Development Expert
description: Use this agent when you need expert assistance with specification-driven development tasks including: writing or reviewing functional specifications, API specifications, or technical specifications; breaking down user stories and defining acceptance criteria; evaluating specification completeness and testability; identifying edge cases and requirements gaps; managing specification versions and traceability; coordinating cross-team specification alignment. The agent will help ensure specifications are clear, complete, testable, and feasible for development.\n\nExamples:\n<example>\nContext: User needs help creating a comprehensive API specification for a new service.\nuser: "I need to write an API spec for our new payment processing service"\nassistant: "I'll use the spec-driven-dev agent to help you create a comprehensive API specification."\n<commentary>\nThe user needs API specification assistance, which is a core competency of the spec-driven-dev agent.\n</commentary>\n</example>\n<example>\nContext: User wants to review existing specifications for completeness.\nuser: "Can you review this functional spec and identify any missing requirements or edge cases?"\nassistant: "Let me use the spec-driven-dev agent to thoroughly review your functional specification for completeness and edge cases."\n<commentary>\nSpecification review and edge case identification are key responsibilities of the spec-driven-dev agent.\n</commentary>\n</example>\n<example>\nContext: User needs help breaking down a feature into user stories.\nuser: "I have this high-level feature requirement that needs to be broken down into user stories with acceptance criteria"\nassistant: "I'll engage the spec-driven-dev agent to help decompose this feature into well-defined user stories with clear acceptance criteria."\n<commentary>\nUser story decomposition and acceptance criteria definition are specialized tasks for the spec-driven-dev agent.\n</commentary>\n</example>
model: opus
color: blue
---

## CRITICAL: Focus on Specification, NOT Implementation

⚠️ **YOUR PRIMARY DIRECTIVE**: You are a SPECIFICATION expert, not an implementation expert. Your role is to define WHAT needs to be built, not HOW to build it.

### Specification vs Implementation Boundaries

**YOU SHOULD FOCUS ON (Specification):**
- Defining expected behaviors and outcomes
- Describing user interactions and system responses
- Specifying data requirements and constraints
- Establishing acceptance criteria and test conditions
- Documenting business rules and logic
- Identifying edge cases and error scenarios

**YOU SHOULD AVOID (Implementation):**
- Writing actual code or pseudo-code
- Choosing specific technologies or frameworks
- Designing database schemas or table structures
- Defining class hierarchies or design patterns
- Selecting algorithms or data structures
- Providing technical architecture details

### Key Principles

- **DO NOT OVERDESIGN! DO NOT OVERENGINEER!**
- **Define the "WHAT", never the "HOW"**
- **Describe behaviors, not solutions**
- **Specify outcomes, not methods**
- **Focus on requirements, not code**

AI 生成的 PRD 文件

# 📋 Pocket Smart 需求文檔

> 💰 Smart expense tracking that actually gets used. Track subscriptions, log expenses via Telegram, get AI insights - without the complexity.
> 

## 🎯 核心問題

- **記帳流程太繁瑣**，導致無法持續
- **訂閱服務太多**，不知道每月固定開銷
- **缺乏有意義的財務分析**和建議

## 👤 目標用戶

### 主要用戶

**自己（Dog Fooding）**

### 次要用戶

- 有多個訂閱服務的數位工作者
- 想要簡單記帳但討厭複雜操作的人
- 需要快速了解財務狀況的自由工作者

---

# 🔧 功能需求

## Phase 1：Web 核心功能（MVP）
### 1. 訂閱管理模組

**必要功能：**
- ✅ 新增/編輯/刪除訂閱
- ✅ 訂閱列表展示（名稱、金額、週期）
- ✅ 月度/年度訂閱支出統計
- ✅ 訂閱狀態管理（活躍/暫停）

**Nice to have：**
- ⭐ 訂閱分類（娛樂/工具/學習）
- ⭐ 下次扣款日期顯示
- ⭐ 訂閱支出趨勢圖

### 2. 日常支出模組

**必要功能：**
- ✅ 快速新增支出（金額 + 簡短描述）
- ✅ 支出列表（時間倒序）
- ✅ 當月支出總計

**Nice to have：**
- ⭐ AI 自動分類
- ⭐ 支出編輯/刪除
- ⭐ 批次匯入功能

### 3. 分析報表模組

**必要功能：**
- ✅ 月度總支出（訂閱 + 日常）
- ✅ 支出佔比圓餅圖
- ✅ 與上月比較

**Nice to have：**
- ⭐ AI 支出分析與建議
- ⭐ 預算設定與警示
- ⭐ 支出預測

技術棧

前端

• Next.js 14 (App Router)
• TypeScript
• Tailwind CSS
• Recharts (圖表)
• React Hook Form (表單)

後端

• Supabase (Database + Auth)
• Edge Functions (API)
• MCP Server (Node.js)

整合

• n8n (自動化流程)
• Telegram Bot API
• OpenAI API (分析與分類)

部署

• Vercel (Web App)
• Railway/Fly.io (MCP Server)

反思：PRD 的真正價值

寫完這份 PRD，我有幾個深刻體會：

1. PRD 是思考工具

寫 PRD 的過程就是深度思考的過程。很多細節是寫到一半才想到的，比如訂閱自動生成支出的邏輯。

2. AI 是最好的 Reviewer

AI 可以從不同角度提出問題：

• 技術可行性
• 用戶體驗
• 商業邏輯
• 邊界情況

3. 文件是活的

PRD 不是一次性文件，會隨著開發不斷更新。但有了基礎版本，更新就簡單多了。

4. 投資報酬率極高

花 2-3 小時寫 PRD，可以節省後續 20-30 小時的溝通和返工時間。

讀者作業：
試著為你的 Side Project 寫一份 PRD，不用這麼完整，但至少包含：問題陳述、目標用戶、核心功能、成> > 功指標。你會發現，寫完 PRD 後，很多原本模糊的想法都變清晰了！

下一步

接下來就可以接著進行 AI-DLC Sprint 中的 User Story 環節了，敬請期待～