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AgCel

c4-context

C4 Context Level: System Context

Section titled “C4 Context Level: System Context”

Use this skill when

Section titled “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

Section titled “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

Section titled “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

Section titled “System Overview”

Short Description

Section titled “Short Description”

[One-sentence description of what the system does]

Long Description

Section titled “Long Description”

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

Personas

Section titled “Personas”

[Persona Name]

Section titled “[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

Section titled “System Features”

[Feature Name]

Section titled “[Feature Name]”
  • Description: [What this feature does]
  • Users: [Which personas use this feature]
  • User Journey: [Link to user journey map]

User Journeys

Section titled “User Journeys”

[Feature Name] - [Persona Name] Journey

Section titled “[Feature Name] - [Persona Name] Journey”
  3. …

[External System] Integration Journey

Section titled “[External System] Integration Journey”
  2. …

External Systems and Dependencies

Section titled “External Systems and Dependencies”

[External System Name]

Section titled “[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

Section titled “System Context Diagram”

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

Section titled “Related 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):

  • 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

Section titled “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

Section titled “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

Section titled “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

Gap Analysis Rule

Section titled “Gap Analysis Rule”

Always identify gaps and suggest next steps to users. In case there is no gaps anymore, then AI should clearly state that there is no gap left.