/c4-context

name: c4-context
description: Expert C4 Context-level documentation specialist. Creates high-level system context diagrams, documents personas, user journeys, system features, and external dependencies.
risk: unknown
source: community
date_added: '2026-02-27'

C4 Context Level: System Context

Use this skill when

• Working on c4 context level: system context tasks or workflows
• Needing guidance, best practices, or checklists for c4 context level: system context

Do not use this skill when

• The task is unrelated to c4 context level: system context
• 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`.

System Overview

Short Description

[One-sentence description of what the system does]

Long Description

[Detailed description of the system's purpose, capabilities, and the problems it solves]

Personas

[Persona Name]

• **Type**: [Human User / Programmatic User / External System]
• **Description**: [Who this persona is and what they need]
• **Goals**: [What this persona wants to achieve]
• **Key Features Used**: [List of features this persona uses]

System Features

[Feature Name]

• **Description**: [What this feature does]
• **Users**: [Which personas use this feature]
• **User Journey**: [Link to user journey map]

User Journeys

[Feature Name] - [Persona Name] Journey

1. [Step 1]: [Description] 2. [Step 2]: [Description] 3. [Step 3]: [Description] ...

[External System] Integration Journey

1. [Step 1]: [Description] 2. [Step 2]: [Description] ...

External Systems and Dependencies

[External System Name]

• **Type**: [Database, API, Service, Message Queue, etc.]
• **Description**: [What this external system provides]
• **Integration Type**: [API, Events, File Transfer, etc.]
• **Purpose**: [Why the system depends on this]

System Context Diagram

[Mermaid diagram showing system, users, and external systems]

Related Documentation

• Container Documentation
• Component Documentation

## Context Diagram Template

According to the [C4 model](https://c4model.com/diagrams/system-context), a System Context diagram shows the system as a box in the center, surrounded by its users and the other systems that it interacts with. The focus is on **people (actors, roles, personas) and software systems** rather than technologies, protocols, and other low-level details.

Use proper Mermaid C4 syntax:

```mermaid
C4Context
    title System Context Diagram

    Person(user, "User", "Uses the system to accomplish their goals")
    System(system, "System Name", "Provides features X, Y, and Z")
    System_Ext(external1, "External System 1", "Provides service A")
    System_Ext(external2, "External System 2", "Provides service B")
    SystemDb(externalDb, "External Database", "Stores data")

    Rel(user, system, "Uses")
    Rel(system, external1, "Uses", "API")
    Rel(system, external2, "Sends events to")
    Rel(system, externalDb, "Reads from and writes to")

**Key Principles** (from [c4model.com](https://c4model.com/diagrams/system-context)):

• Focus on **people and software systems**, not technologies
• Show the **system boundary** clearly
• Include all **users** (human and programmatic)
• Include all **external systems** the system interacts with
• Keep it **stakeholder-friendly** - understandable by non-technical audiences
• Avoid showing technologies, protocols, or low-level details

Example Interactions

• "Create C4 Context-level documentation for the system"
• "Identify all personas and create user journey maps for key features"
• "Document external systems and create a system context diagram"
• "Analyze system documentation and create comprehensive context documentation"
• "Map user journeys for all key features including programmatic users"

Key Distinctions

• **vs C4-Container agent**: Provides high-level system view; Container agent focuses on deployment architecture
• **vs C4-Component agent**: Focuses on system context; Component agent focuses on logical component structure
• **vs C4-Code agent**: Provides stakeholder-friendly overview; Code agent provides technical code details

Output Examples

When creating context documentation, provide:

• Clear system descriptions (short and long)
• Comprehensive persona documentation (human and programmatic)
• Complete feature lists with descriptions
• Detailed user journey maps for all key features
• Complete external system and dependency documentation
• Mermaid context diagram showing system, users, and external systems
• Links to container and component documentation
• Stakeholder-friendly documentation understandable by non-technical audiences
• Consistent documentation format

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.