Domain Expert Skill

Purpose

Discover, learn, and guide domain knowledge. Helps understand project concepts, terminology, and how to map requests to domain patterns.

Quick Reference

• Provides: Domain knowledge, concept explanations, request mapping
• Modes: configure, learn, explain, map

Modes Overview

Configure Mode: /domain configure (Setup)

Discovers domain knowledge from existing documentation.

/domain configure

What it checks:

• CLAUDE.md (Domain section)
• README.md (Project overview)
• docs/domain.md, docs/glossary.md
• docs/ADR/*.md (Architecture Decision Records)

Output:

## Discovered Domain Knowledge

**Project:** E-commerce platform
**Confidence:** High (domain.md found)

### Glossary (12 terms)
| Term | Definition |
|------|------------|
| Customer | User who has made a purchase |
| Order | Customer's request to purchase items |
| Cart | Collection of items before checkout |

### Entities (5 found)
| Entity | Description | Key Attributes |
|--------|-------------|----------------|
| Customer | Registered user | id, email, tier |
| Order | Purchase request | id, status, items |

### Business Rules (3 found)
| Rule | Context |
|------|---------|
| Orders can only be cancelled within 24h | Order cancellation |

**Save this configuration?** [Confirm / Adjust]

Learn Mode: /domain learn

Analyzes domain code to infer entities, relationships, and patterns.

# Analyze all domain code (default)
/domain learn --analyze

# Learn from specific file
/domain learn --from src/domain/order/order.ts

What it analyzes by language:

Output:

## Inferred Domain Knowledge

**Method:** Code analysis (23 files)
**Confidence:** Medium

### Entities (inferred)
| Name | Type | Attributes | Confidence |
|------|------|------------|------------|
| User | Entity | id, email, status | 95% |
| Order | Aggregate | id, items, total | 90% |
| Money | Value Object | amount, currency | 85% |

### Relationships

User ──1:N──> Order Order ──1:N──> OrderItem OrderItem ──N:1──> Product

### Naming Patterns
- Entities: PascalCase nouns (User, Order)
- Events: PascalCase past tense (OrderCreated)
- Commands: PascalCase imperative (CreateOrder)

**Save this configuration?** [Confirm / Adjust]

Explain Mode: /domain explain <concept>

Explains a domain concept with full context.

/domain explain Order
/domain explain "value object"

Output:

## Domain Concept: Order

**Definition:** A customer's request to purchase one or more products.

**Type:** Aggregate Root

**Attributes:**
- id: Unique order identifier
- status: pending, confirmed, shipped, delivered, cancelled
- items: List of OrderItems
- total: Calculated total (Money)

**Relationships:**
- Belongs to: Customer
- Contains: OrderItem (1:N)

**Business Rules:**
- Cannot be modified after shipping
- Can only be cancelled within 24 hours
- Total must equal sum of items

**Code Location:** src/domain/order/order.ts

Map Mode: /domain map <request>

Maps a user request to domain concepts (used by developer skill).

/domain map "Allow users to cancel orders and get refunds"

Output:

## Domain Mapping

**Request:** "Allow users to cancel orders and get refunds"

### Entities Involved
| Entity | Role |
|--------|------|
| User | Actor (who cancels) |
| Order | Target (what's cancelled) |
| Payment | Related (what's refunded) |

### Operations
| Operation | Type | Description |
|-----------|------|-------------|
| CancelOrder | Command | Change order status to cancelled |
| RefundPayment | Command | Initiate refund for payment |
| OrderCancelled | Event | Emitted after cancellation |

### Business Rules
- Can only cancel orders in pending/confirmed status
- Refund amount depends on cancellation timing
- Must notify customer of cancellation

### Code Locations
- Order: src/domain/order/order.ts
- Payment: src/domain/payment/payment.ts

DDD Building Blocks

The skill categorizes discovered concepts using DDD patterns:

Configuration

Config Location

Config path depends on how the plugin was installed:

Precedence when reading (first found wins):

1. .claude/skills/domain-expert.local.yaml
2. .claude/skills/domain-expert.yaml
3. Skill defaults

Integration

The domain-expert skill integrates with:

• developer - Uses /domain map to understand requests
• arch - Domain is typically the innermost layer
• code - Domain code follows specific patterns