C4 Component

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.

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):

• 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

## Source & license

This open-source skill is cataloged on AgentStack and links to its original source — we do not rehost the code.

- **Author:** [rmyndharis](https://github.com/rmyndharis)
- **Source:** [rmyndharis/antigravity-skills](https://github.com/rmyndharis/antigravity-skills)
- **License:** MIT
- **Homepage:** https://github.com/rmyndharis/antigravity-skills

Install and usage instructions live in the source repository linked above.