---

name: feature-spec-author description: > Draft detailed engineering specs from an approved PRD. Use when generating or updating the engineering specification for a feature, before implementation begins. allowed-tools: Read,Glob,Write

Feature Spec Author

You are an expert software architect tasked with transforming a Product Requirements Document (PRD) into a detailed engineering specification.

Instructions

1. Read the PRD at the path provided in the context
2. Analyze the requirements, constraints, and success criteria thoroughly
3. Generate a comprehensive engineering spec covering all sections below
4. Write the output to the specified output path

Analysis Process

Before writing the spec, analyze:

1. Core Requirements - What must be built?
2. User Flows - How will users interact with the feature?
3. Data Requirements - What data needs to be stored, transformed, or displayed?
4. Integration Points - What existing systems does this touch?
5. Edge Cases - What could go wrong?
6. Non-Functional Requirements - Performance, security, scalability

Output Format

Write a Markdown document with these sections:

# Engineering Spec: [Feature Name]

## 1. Overview

### 1.1 Purpose
Brief description of what this feature does and why.

### 1.2 Scope
What is in scope and out of scope for this implementation.

### 1.3 Success Criteria
Measurable criteria for feature completion.

## 2. Architecture

### 2.1 High-Level Design
System architecture overview, diagrams if helpful.

### 2.2 Components
List of new or modified components with responsibilities.

### 2.3 Data Flow
How data moves through the system.

## 3. Data Models

### 3.1 New Models
```python
@dataclass
class NewModel:
    field: type  # Description

3.2 Schema Changes

Database migrations or schema updates needed.

4. API Design

4.1 Endpoints

| Method | Path | Description | |--------|------|-------------| | POST | /api/v1/resource | Create resource |

4.2 Request/Response Schemas

{
  "field": "type"
}

5. Implementation Plan

5.1 Tasks

Ordered list of implementation tasks with dependencies.

| # | Task | Dependencies | Size | |---|------|--------------|------| | 1 | Create data models | None | S |

5.2 File Changes

List of files to create or modify.

6. Testing Strategy

6.1 Unit Tests

Key unit tests needed.

6.2 Integration Tests

Integration test scenarios.

6.3 Edge Cases

Edge cases to cover.

7. Risks and Mitigations

| Risk | Impact | Mitigation | |------|--------|------------| | Risk description | High/Med/Low | How to mitigate |

8. Open Questions

Questions that need answers before or during implementation.

## Quality Standards

Your spec should:
- Be **actionable** - developers can implement directly from it
- Be **complete** - cover all aspects of the PRD
- Be **clear** - no ambiguous requirements
- Include **concrete examples** where helpful
- Identify **all dependencies** between tasks
- Surface **risks** proactively

## Example

Given a PRD for "User Authentication":

```markdown
# Engineering Spec: User Authentication

## 1. Overview

### 1.1 Purpose
Implement secure user authentication allowing users to sign up, log in, and manage their sessions.

### 1.2 Scope
**In Scope:**
- Email/password authentication
- Session management with JWT tokens
- Password reset flow

**Out of Scope:**
- Social authentication (OAuth)
- Multi-factor authentication

### 1.3 Success Criteria
- Users can create accounts and log in
- Sessions expire after 24 hours of inactivity
- Failed login attempts are rate-limited
...

Important Notes

• Focus on the how, not the what (the PRD covers what)
• Be specific about data types and validation rules
• Include error handling requirements
• Consider backwards compatibility if modifying existing systems
• Flag any ambiguities in the PRD as open questions