Spec Builder

Spec Generator Skill

Generate a complete specification suite that transforms ideas into actionable implementation plans.

Purpose

This skill helps you create professional, comprehensive specification documents that include:

1. Requirements (requirements.md) - User stories with acceptance criteria
2. Technical Design (design.md) - Architecture, components, and interactions
3. Task Breakdown (tasks.md) - Granular, actionable implementation tasks

Perfect for product teams, developers, and AI coding agents to understand requirements, system architecture, and execution steps.

📋 Phase 1: REQUIREMENTS Generation

Objective

Create clear, testable requirements using user stories and acceptance criteria.

Instructions

1. Identify the Core User Story

   • Write in format: "As a [user], I want to [action], so that [benefit]"
   • Focus on user value, not implementation

2. Define Acceptance Criteria using EARS Format

   • Use WHEN/THEN structure for clarity
   • Make criteria specific and testable
   • Cover both success and failure scenarios

3. Specify Constraints and Boundaries

   • Input requirements and validation rules
   • Output expectations
   • Performance requirements
   • Security considerations
   • Error handling requirements

Template Structure

# Requirements: [Feature Name]

## Overview
Brief description of what this feature does and why it matters.

## User Stories

### Story 1: [Title]
**As a** [user type]
**I want** [action]
**So that** [benefit]

### Story 2: [Title]
...

## Acceptance Criteria

### Criterion 1: [Name]
**WHEN** [trigger condition or scenario]
**THE SYSTEM SHALL** [expected behavior]

**GIVEN** [precondition]
**WHEN** [action]
**THEN** [expected outcome]

### Criterion 2: [Name]
...

## Constraints & Requirements

### Functional Requirements
- REQ-001: [Requirement description]
- REQ-002: ...

### Non-Functional Requirements
- Performance: [specific metrics]
- Security: [security requirements]
- Scalability: [scalability needs]

### Input Requirements
- Input format: [specification]
- Validation rules: [rules]
- Data sources: [sources]

### Output Requirements
- Output format: [specification]
- Success conditions: [conditions]
- Failure conditions: [conditions]

## Edge Cases
1. [Edge case 1]
2. [Edge case 2]
...

## Out of Scope
- [What this feature explicitly does NOT include]

🏗️ Phase 2: DESIGN Generation

Objective

Create a technical design that shows HOW the system will work.

Instructions

1. High-Level Architecture

   • Describe the overall system structure
   • Identify major components and their roles
   • Show data flow and integration points

2. Component Design

   • Break down into logical modules/components
   • Define responsibilities for each component
   • Specify interfaces and contracts

3. Interaction Design

   • Create sequence diagrams (text format)
   • Show component interactions
   • Define API contracts and data structures

4. Technical Decisions

   • List key technical choices
   • Document trade-offs
   • Explain rationale for decisions

5. Risk Analysis

   • Identify potential risks
   • Suggest mitigation strategies

Template Structure

# Technical Design: [Feature Name]

## Overview
High-level summary of the technical approach.

## Architecture

### System Architecture
[Describe the overall architecture - layers, boundaries, external dependencies]

[Text-based architecture diagram] ┌─────────────┐ │ Frontend │ ├─────────────┤ │ API Layer │ ├─────────────┤ │ Business │ │ Logic │ ├─────────────┤ │ Data │ │ Layer │ └─────────────┘

### Component Breakdown

#### Component A: [Name]
- **Purpose**: [What it does]
- **Responsibilities**: 
  - [Responsibility 1]
  - [Responsibility 2]
- **Dependencies**: [What it depends on]
- **Interfaces**: [Public APIs/methods]

#### Component B: [Name]
...

## Data Model

### Entities

Entity: [Name] Fields:

• field1: type (description)
• field2: type (description) Relationships:
• relationship description

### Data Flow
1. [Step 1: data enters system]
2. [Step 2: transformation]
3. [Step 3: output]

## Sequence Diagrams

### Primary Flow: [Scenario Name]

User → Frontend: [action] Frontend → API: [request] API → Service: [call] Service → Database: [query] Database → Service: [result] Service → API: [response] API → Frontend: [data] Frontend → User: [display]

### Alternative Flow: [Scenario Name]
...

## API Contracts

### Endpoint 1: [Name]
- **Method**: POST/GET/etc
- **Path**: /api/v1/resource
- **Request Body**:
```json
{
  "field1": "type",
  "field2": "type"
}

• Response:

{
  "status": "success",
  "data": {}
}

• Error Codes: 400, 401, 500

Endpoint 2: [Name]

...

Technical Decisions

Decision 1: [Title]

• Context: [Why this decision is needed]
• Options Considered:
  1. Option A: [pros/cons]
  2. Option B: [pros/cons]
• Decision: [Chosen option]
• Rationale: [Why this was chosen]
• Trade-offs: [What we're accepting]

Decision 2: [Title]

...

Error Handling Strategy

• [How errors are caught and handled]
• [Logging strategy]
• [User-facing error messages]

Security Considerations

• Authentication: [approach]
• Authorization: [approach]
• Data protection: [approach]
• Input validation: [approach]

Performance Considerations

• Expected load: [metrics]
• Optimization strategy: [approach]
• Caching strategy: [if applicable]
• Database indexing: [if applicable]

Risks & Mitigations

Risk 1: [Title]

• Impact: High/Medium/Low
• Probability: High/Medium/Low
• Mitigation: [Strategy]

Risk 2: [Title]

...

Future Considerations

• [What might change]
• [Extensibility points]
• [Technical debt to consider]

---

## ✅ Phase 3: TASK BREAKDOWN Generation

### Objective
Break down the design into granular, actionable tasks suitable for implementation.

### Instructions

1. **Create Sequential Tasks**
   - Order tasks by dependencies
   - Each task should be completable independently once dependencies are met
   - Aim for tasks that take 2-8 hours

2. **For Each Task Include**:
   - Clear description of what needs to be done
   - Expected output/deliverable
   - Input requirements
   - Dependencies on other tasks
   - Acceptance criteria for completion
   - Complexity/time estimate (optional)

3. **Organize by Categories**:
   - Data/Schema tasks
   - Backend/API tasks
   - Frontend/UI tasks
   - Integration tasks
   - Testing tasks
   - Documentation tasks

4. **Review and Organize Tasks**:
   - Ensure tasks are properly sequenced by dependencies
   - Verify each task has clear acceptance criteria
   - Confirm tasks are appropriately sized (2-8 hours each)

### Template Structure

```markdown
# Task Breakdown: [Feature Name]

## Task Overview
Total estimated tasks: [number]
Estimated total effort: [time/complexity]

## Task Dependencies Graph

Task 1 → Task 3 → Task 5 Task 2 → Task 4 → Task 5

---

## 📦 Phase 1: Foundation Tasks

### Task #1: [Task Title]

**Category**: Data/Schema

**Description**:
[Detailed description of what needs to be done]

**Expected Output**:
- [Deliverable 1: e.g., schema.json file]
- [Deliverable 2: e.g., migration script]

**Input Requirements**:
- [What you need before starting]

**Dependencies**:
- None (or list dependent tasks)

**Acceptance Criteria**:
- [ ] [Criterion 1]
- [ ] [Criterion 2]
- [ ] [Criterion 3]

**Complexity**: Low/Medium/High
**Estimated Time**: [2-4 hours]

**Implementation Notes**:
- [Any specific guidance]
- [Gotchas to watch out for]

---

### Task #2: [Task Title]
...

## 📦 Phase 2: Backend/API Tasks

### Task #3: [Task Title]
...

## 📦 Phase 3: Frontend/UI Tasks

### Task #5: [Task Title]
...

## 📦 Phase 4: Integration Tasks

### Task #7: [Task Title]
...

## 📦 Phase 5: Testing Tasks

### Task #9: [Task Title]

**Category**: Testing

**Description**:
Write unit tests for [component]

**Expected Output**:
- Test file with >80% coverage
- All edge cases covered

**Test Cases**:
1. [Test case 1]
2. [Test case 2]
...

---

## 📦 Phase 6: Documentation & Deployment

### Task #11: [Task Title]
...

---

## Summary

### Critical Path
[List the sequence of tasks that must be completed in order]

### Parallel Work Opportunities
[Tasks that can be done simultaneously]

### Risk Items
[Tasks with high uncertainty or complexity]

### Definition of Done
- [ ] All tasks completed
- [ ] All tests passing
- [ ] Documentation updated
- [ ] Code reviewed
- [ ] Deployed to staging

🚀 Usage Instructions

How to Use This Skill

1. Provide the Feature Request

   • Describe what you want to build
   • Include any context, constraints, or requirements
   • Mention target users and use cases

2. Let the Skill Work

   • The skill will guide you through all three phases
   • Ask clarifying questions if needed
   • Iterate on each document

3. Review and Refine

   • Review generated documents
   • Request modifications or additions
   • Ensure all stakeholders understand

4. Track Implementation Progress

   • Use the generated tasks as a checklist
   • Mark tasks as completed as you implement them
   • Update task status and notes as needed

Example Invocation

Use spec-builder to generate a full spec for:
"Implement user authentication with 2FA, email verification, 
and session expiry handling in our web app."

What You'll Get

After running this skill, you'll have three comprehensive documents:

1. requirements.md - Clear user stories and acceptance criteria
2. design.md - Technical architecture and component design
3. tasks.md - Detailed implementation tasks ready for developers

These documents are optimized for:

• Human developers to understand the system
• AI coding agents (Cursor, Copilot) to implement tasks
• Product teams to validate requirements
• Stakeholders to review scope and approach

💡 Best Practices

When Creating Requirements

• Focus on WHAT, not HOW
• Make acceptance criteria testable
• Include both positive and negative cases
• Consider accessibility and internationalization

When Creating Design

• Start high-level, then drill down
• Document WHY decisions were made
• Consider scalability from the start
• Think about error cases and edge conditions

When Creating Tasks

• Keep tasks small and focused
• Make dependencies explicit
• Include clear acceptance criteria
• Provide enough context for independent work

Quality Checklist

• ✅ Can a developer implement this without asking questions?
• ✅ Can QA create test cases from the requirements?
• ✅ Can an AI agent understand the task breakdown?
• ✅ Are trade-offs and risks documented?
• ✅ Is the scope clear (what's included and excluded)?

📝 Output File Organization

After running this skill, organize output files as:

project-root/
├── .claude/
│   └── specs/
│       └── [feature-name]/
│           ├── requirements.md
│           ├── design.md
│           └── tasks.md

Or place them in a dedicated specs directory:

project-root/
├── docs/
│   └── specs/
│       └── [feature-name]/
│           ├── requirements.md
│           ├── design.md
│           └── tasks.md

� Iteratrion and Updates

This skill can also help you:

• Refine existing specs: Provide an existing spec document and ask to improve it
• Update for changes: When requirements change, update all three documents
• Generate partial specs: Only generate requirements or design if that's what you need
• Compare approaches: Generate multiple design options for evaluation

🎯 Success Metrics

A good spec generated by this skill should:

1. Be Complete: Cover all aspects from requirements to implementation
2. Be Clear: Anyone can understand without additional context
3. Be Actionable: Tasks can be implemented immediately
4. Be Testable: Acceptance criteria are specific and measurable
5. Be Maintainable: Easy to update as requirements evolve

Example Output Snippets

Requirements Example

## User Story
**As a** registered user
**I want** to enable 2FA for my account
**So that** my account is more secure

## Acceptance Criteria
**WHEN** a user enables 2FA
**THE SYSTEM SHALL** generate a QR code with TOTP secret

**GIVEN** 2FA is enabled
**WHEN** user logs in with correct password
**THEN** system prompts for 6-digit code
**AND** code must be entered within 30 seconds

Design Example

## Component: AuthenticationService
**Purpose**: Handle user authentication flows

**Responsibilities**:
- Verify user credentials
- Manage 2FA enrollment and verification
- Handle session creation and expiry

**Interface**:
- `login(username, password): SessionToken`
- `verify2FA(userId, code): boolean`
- `enrollIn2FA(userId): QRCode`

Task Example

### Task #3: Implement 2FA Enrollment API

**Description**: Create API endpoint for users to enroll in 2FA

**Expected Output**:
- POST /api/v1/auth/2fa/enroll endpoint
- Returns QR code and backup codes
- Stores TOTP secret securely

**Acceptance Criteria**:
- [ ] Endpoint returns 200 with QR code data
- [ ] Secret is encrypted before storage
- [ ] 10 backup codes generated
- [ ] Rate limiting applied (5 requests/hour)

🆘 Troubleshooting

Q: The generated spec is too detailed A: Ask to generate a "lightweight" or "minimal" version

Q: Need more technical depth A: Request "detailed technical design with code examples"

Q: Tasks are too large A: Ask to "break down tasks into smaller sub-tasks of 2-4 hours each"

Q: Need specific format A: Specify your organization's format: "Use our company's standard template"

Version History

• v1.0.0 (2025-12-20): Initial release with three-phase spec generation

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