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

●[Feature 1]: [Description]

●[Feature 2]: [Description]

●[Feature 3]: [Description]

Code Elements

This component contains the following code-level elements:

●[c4-code-file-1.md](./c4-code-file-1.md) - [Description]

●[c4-code-file-2.md](./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

c4-component

Documentation