C4 Component Level: [Component Name]
Use this skill when
- Working on c4 component level: [component name] tasks or workflows
- Needing guidance, best practices, or checklists for c4 component level: [component name]
Do not use this skill when
- The task is unrelated to c4 component level: [component name]
- You need a different domain or tool outside this scope
Instructions
- Clarify goals, constraints, and required inputs.
- Apply relevant best practices and validate outcomes.
- Provide actionable steps and verification.
- If detailed examples are required, open
resources/implementation-playbook.md.
Overview
- Name: [Component name]
- Description: [Short description of component purpose]
- Type: [Component type: Application, Service, Library, etc.]
- Technology: [Primary technologies used]
Purpose
[Detailed description of what this component does and what problems it solves]
Software Features
- - -
Code Elements
This component contains the following code-level elements:
- c4-code-file-1.md - [Description]
- c4-code-file-2.md - [Description]
Interfaces
[Interface Name]
- Protocol: [REST/GraphQL/gRPC/Events/etc.]
- Description: [What this interface provides]
- Operations:
- operationName(params): ReturnType - [Description]
Dependencies
Components Used
- [Component Name]: [How it's used]
External Systems
- [External System]: [How it's used]
Component Diagram
Use proper Mermaid C4Component syntax. Component diagrams show components within a single container:
C4Component
title Component Diagram for [Container Name]
Container_Boundary(container, "Container Name") {
Component(component1, "Component 1", "Type", "Description")
Component(component2, "Component 2", "Type", "Description")
ComponentDb(component3, "Component 3", "Database", "Description")
}
Container_Ext(externalContainer, "External Container", "Description")
System_Ext(externalSystem, "External System", "Description")
Rel(component1, component2, "Uses")
Rel(component2, component3, "Reads from and writes to")
Rel(component1, externalContainer, "Uses", "API")
Rel(component2, externalSystem, "Uses", "API")**Key Principles** (from [c4model.com](https://c4model.com/diagrams/component)):
- Show components **within a single container** (zoom into one container)
- Focus on **logical components** and their responsibilities
- Show **component interfaces** (what they expose)
- Show how components **interact** with each other
- Include **external dependencies** (other containers, external systems)Master Component Index Template
# C4 Component Level: System Overview
## System Components
### [Component 1]
- **Name**: [Component name]
- **Description**: [Short description]
- **Documentation**: [c4-component-name-1.md](./c4-component-name-1.md)
### [Component 2]
- **Name**: [Component name]
- **Description**: [Short description]
- **Documentation**: [c4-component-name-2.md](./c4-component-name-2.md)
## Component Relationships
[Mermaid diagram showing all components and their relationships]Example Interactions
- "Synthesize all c4-code-*.md files into logical components"
- "Define component boundaries for the authentication and authorization code"
- "Create component-level documentation for the API layer"
- "Identify component interfaces and create component diagrams"
- "Group database access code into components and document their relationships"
Key Distinctions
- vs C4-Code agent: Synthesizes multiple code files into components; Code agent documents individual code elements
- vs C4-Container agent: Focuses on logical grouping; Container agent maps components to deployment units
- vs C4-Context agent: Provides component-level detail; Context agent creates high-level system diagrams
Output Examples
When synthesizing components, provide:
- Clear component boundaries with rationale
- Descriptive component names and purposes
- Comprehensive feature lists for each component
- Complete interface documentation with protocols and operations
- Links to all contained c4-code-*.md files
- Mermaid component diagrams showing relationships
- Master component index with all components
- Consistent documentation format across all components