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

### [Component 2]
- **Name**: [Component name]
- **Description**: [Short description]
- **Documentation**: 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

Limitations

Use this skill only when the task clearly matches the scope described above.
Do not treat the output as a substitute for environment-specific validation, testing, or expert review.
Stop and ask for clarification if required inputs, permissions, safety boundaries, or success criteria are missing.

C4 Component