generate-usecase-diagram

name	generate-usecase-diagram
description	Generate use case diagram in Mermaid format from business requirements. Use when user needs to visualize actors, use cases, and system boundaries for a feature or when PRD diagrams are requested.
argument-hint	<requirements-description> [--ci]
license	MIT
user-invocable	true
context	fork
agent	haiku
allowed-tools	Read, Glob, Grep, AskUserQuestion
disallowed-tools	Write, Edit, Bash

Generate Use Case Diagram

Generates a use case diagram in Mermaid flowchart format from business requirements or feature name.

Prerequisites

Read the following reference guides before generation:

• references/usecase_diagram_guide.md - Use case diagram notation and examples
• references/mermaid_notation_rules.md - Mermaid flowchart syntax and styling
• references/output_format_example.md - Exact markdown structure to return

Hybrid Approach

This skill operates in two modes:

Mode	Behavior	Description
Interactive (default)	Guide	May ask clarifying questions, provides detailed output
CI (--ci)	Silent	No user interaction, concise output for pipeline integration

Input

$ARGUMENTS

Argument	Required	Description
requirements-description	Yes	Business requirements text OR feature name
--ci	-	CI/non-interactive mode. Skips clarifying questions

When feature name is provided, look for existing PRD at ${CLAUDE_PROJECT_DIR}/${SDD_REQUIREMENT_PATH}/{feature-name}.md.

Input Examples

Feature name (looks up PRD): /generate-usecase-diagram user-authentication

Requirements description: /generate-usecase-diagram Users can register, login, and reset passwords. Admin can manage user accounts.

CI mode (called by generate-prd): /generate-usecase-diagram user-authentication --ci

Generation Flow

Interactive Mode (Default)

1. Analyze Input: Extract actors, use cases, and relationships
2. Clarify (if needed): Ask user about ambiguous requirements
3. Read References: Load diagram guides for correct syntax
4. Generate Diagram: Create Mermaid flowchart with proper styling
5. Validate: Check Quality Checks items
   • If issues found: Fix and repeat from step 4
6. Return Text: Output diagram and documentation (no file write)

CI Mode (--ci)

Skips step 2 (Clarify). Does not use AskUserQuestion tool.

1. Analyze Input: Extract actors, use cases, and relationships
2. Read References: Load diagram guides for correct syntax
3. Generate Diagram: Create Mermaid flowchart with proper styling
4. Validate: Check Quality Checks items
   • If issues found: Fix and repeat from step 3
5. Return Text: Output diagram only (minimal documentation)

Output Format

IMPORTANT: This skill returns text only. It does NOT write files.

See references/output_format_example.md for the exact markdown structure to return (diagram section, Actors table, Use Cases table).

Quality Checks

Before returning, verify:

• All actors from requirements are represented
• All major functions are captured as use cases
• System boundary defined
• Mermaid syntax is valid
• Consistent styling applied

Notes

Diagram Design

• Use consistent granularity within the diagram
• Keep diagram readable by limiting to 7-10 use cases per diagram
• For large systems, create separate diagrams per subsystem or feature group
• Actors represent roles (e.g., "Admin", "Guest"), not specific users

Relationships

• Include: Always executed as part of the base use case (mandatory)
• Extend: Optional behavior that may or may not occur
• Avoid deep nesting of include/extend relationships (max 2 levels)

Naming Conventions

• Use verb phrases for use cases (e.g., "Login", "Register Account")
• Use noun phrases for actors (e.g., "User", "System Administrator")
• Keep names concise but descriptive

Integration

• This skill is typically called by /generate-prd --ci with --ci flag
• Output is text only; the caller is responsible for file operations
• When called standalone (Interactive mode), suggest next step: /analyze-requirements
• In CI mode, output is optimized for pipeline consumption (minimal text, diagram focus)