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Agent skill

C4 Architecture Documentation

by Hack23 in Hack23/cia

Document system architecture using C4 model: context, container, component, code diagrams per ARCHITECTURE.md

Apache-2.0Auto-check passedDevelopment

Install C4 Architecture Documentation

skills CLI
$ npx skills add Hack23/cia --skill c4-architecture-documentation -a claude-code

Project install by default; add -g for ~/.claude/skills/.

GitHub CLI
$ gh skill install Hack23/cia c4-architecture-documentation --agent claude-code

Project scope by default; add --scope user for a personal install. Needs GitHub CLI 2.90.0 or later (public preview).

Manual copy
$ git clone --depth 1 https://github.com/Hack23/cia.git skills-src && mkdir -p .claude/skills && cp -r skills-src/.github/skills/c4-architecture-documentation .claude/skills/c4-architecture-documentation && rm -rf skills-src

Use ~/.claude/skills/ instead of .claude/skills for a personal install. The folder must contain SKILL.md.

Claude Code skills documentation · loads skills from .claude/skills/

Facts

Skill name
c4-architecture-documentation
GitHub stars
239
Token cost
~511 tokens
SKILL.md length
57 words
Files
1
Skills in repo
78
Repo updated
First seen
Licence
Apache-2.0

At a glance

Document system architecture using C4 model: context, container, component, code diagrams per ARCHITECTURE.md

  • Tasks that involve Diagrams
  • SKILL.md covers Purpose, When to Use, C4 Model Levels and PlantUML Diagrams, plus 1 more section
  • Reaches raw.githubusercontent.com

What it does

C4 Architecture Documentation is an agent skill from Hack23/cia. Document system architecture using C4 model: context, container, component, code diagrams per ARCHITECTURE.md

Its SKILL.md is about 510 tokens, which your agent loads only when the skill is triggered. It is a single SKILL.md file with no bundled scripts.

It sits in Development, covering Diagrams. The repository describes itself as: Citizen Intelligence Agency. Open-source intelligence platform analyzing Swedish political activities using AI and data visualization. Tracks politicians, government… The licence is Apache-2.0.

When your agent uses it

  • Tasks that involve Diagrams

Example prompts

  • “/c4-architecture-documentation”

What it can do on your machine

Read from SKILL.md and the folder at commit 6a9797b. It shows what the files ask for, not the result of running them.

  • Tool permissions

    Pre-approves nothing: there is no allowed-tools line, so your agent's usual permission prompts apply.

    From allowed-tools in the SKILL.md frontmatter.

  • Runs code

    No scripts in the folder and no shell commands in SKILL.md (its code samples are java and plantuml).

    From the folder's file list and the shell code blocks in SKILL.md.

  • Network

    Hosts in commands or code, which the agent is likely to contact:

    • raw.githubusercontent.com

    Also links to:

    • c4model.com

    From URLs in SKILL.md, links to its own repository left out.

  • Credentials

    Names no API keys, tokens, secrets or passwords.

    From names ending in _API_KEY, _TOKEN, _SECRET, _KEY or _PASSWORD in SKILL.md.

Context cost

C4 Architecture Documentation loads about 511 tokens when it runs. Until then it costs about 35 tokens; SKILL.md has 57 words of instructions outside code blocks.

Always · name and description, kept in context so the agent knows when to use it
~35
When it runs · the whole SKILL.md, loaded when a task matches
~511

Estimates: characters ÷ 4, the usual rule of thumb; real counts depend on the model's tokenizer. Scripts and assets cost tokens only if the agent reads them.

Safety

Auto-check passed

The automated check found no risky patterns in SKILL.md.

Automated static check — not a guarantee. Review scripts before installing. It scans the text of SKILL.md for risky patterns (piping downloads into a shell, reading credential files, hidden Unicode, destructive commands); files beside SKILL.md are not scanned.

SKILL.md

The full file from Hack23/cia at commit 6a9797b, republished under its Apache-2.0 licence (© Hack23). 57 words, ~511 tokens.

Download SKILL.mdSave it as .claude/skills/c4-architecture-documentation/SKILL.md (or your agent's skills folder).
name
c4-architecture-documentation
description
Document system architecture using C4 model: context, container, component, code diagrams per ARCHITECTURE.md
license
Apache-2.0

C4 Architecture Documentation Skill

Purpose

Document CIA platform architecture using C4 model for different abstraction levels.

When to Use

  • ✅ Documenting system architecture
  • ✅ Onboarding new developers
  • ✅ Architecture decision records
  • ✅ Security architecture reviews

C4 Model Levels

Level 1: System Context
[External Users] --uses--> [CIA Platform] --uses--> [Riksdagen API]
[CIA Platform] --uses--> [World Bank API]
[CIA Platform] --uses--> [PostgreSQL Database]
Level 2: Container Diagram
[Web Browser] --HTTPS--> [Spring MVC App] --JDBC--> [PostgreSQL]
[Spring MVC App] --HTTPS--> [External APIs]
[Spring MVC App] --uses--> [Redis Cache]
Level 3: Component Diagram
java
// Service Layer Components
@Component PoliticianService --uses--> @Repository PoliticianRepository
@Component VotingAnalysisService --uses--> @Repository VotingRecordRepository
@Component RiksdagenClient --calls--> [External Riksdagen API]
Level 4: Code
java
// Detailed class design
public class PoliticianService {
    private final PoliticianRepository repository;
    private final RiksdagenClient riksdagenClient;
    // Implementation details...
}

PlantUML Diagrams

plantuml
@startuml
!include https://raw.githubusercontent.com/plantuml-stdlib/C4-PlantUML/master/C4_Container.puml

Person(user, "Citizen", "Wants political transparency")
System_Boundary(cia, "CIA Platform") {
    Container(web, "Web Application", "Spring MVC, Vaadin 8", "Provides UI")
    ContainerDb(db, "Database", "PostgreSQL", "Stores data")
}
System_Ext(riksdagen, "Riksdagen API", "Government data")

Rel(user, web, "Uses", "HTTPS")
Rel(web, db, "Reads/Writes", "JDBC")
Rel(web, riksdagen, "Fetches data", "HTTPS/REST")
@enduml

References

© Hack23, Apache-2.0. Rendered from Markdown: HTML in the file is shown as text, images as links, and headings moved down two levels. Raw file

Files

Just SKILL.md in .github/skills/c4-architecture-documentation of Hack23/cia.

Open the folder on GitHubat commit 6a9797b

Compare with similar skills

C4 Architecture Documentation next to the 5 skills that share the most tags, products or categories with it. Stars are the repository's; “used in” counts other GitHub owners with a copy.

C4 Architecture Documentation compared with similar skills
SkillStarsUsed inTokensAuto-checkLicenceRepo updated
C4 Architecture Documentation this skillHack23/cia239—~511Automated safety check: PassApache-2.0
JSON Canvasheyitsnoah/claudesidian2.6k18 repos~3.5kAutomated safety check: PassMIT
Archify Diagramstt-a1i/archify79k—~2.9kAutomated safety check: PassMIT
Diagram Designcathrynlavery/diagram-design44k1 repos~7.5kAutomated safety check: PassMIT
Fireworks Tech Graphtisfeng/Easydict15k1 repos~1.4kAutomated safety check: PassMIT
Excalidraw Diagramcoleam00/excalidraw-diagram-skill4.9k2 repos~6.1kAutomated safety check: PassNone

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  • AWS Cloudwatch Monitoring

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  • AWS Security Architecture

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Categories

Questions about C4 Architecture Documentation

What does C4 Architecture Documentation do?

Document system architecture using C4 model: context, container, component, code diagrams per ARCHITECTURE.md. C4 Architecture Documentation is an agent skill from Hack23/cia.

When should I use C4 Architecture Documentation?

C4 Architecture Documentation fits situations like: tasks that involve Diagrams.

How do I install C4 Architecture Documentation in Claude Code?

Run `npx skills add Hack23/cia --skill c4-architecture-documentation -a claude-code`. Or copy the skill folder (.github/skills/c4-architecture-documentation in Hack23/cia) into .claude/skills/c4-architecture-documentation in your project. Claude Code loads it when a task matches its description.

How do I install C4 Architecture Documentation in Codex?

Run `npx skills add Hack23/cia --skill c4-architecture-documentation -a codex`. Or copy the skill folder (.github/skills/c4-architecture-documentation in Hack23/cia) into .agents/skills/c4-architecture-documentation in your project. Codex loads it when a task matches its description.

Can I use C4 Architecture Documentation in Cursor, Gemini CLI or GitHub Copilot?

Cursor, Gemini CLI, GitHub Copilot and OpenCode also load SKILL.md folders. With the skills CLI, run `npx skills add Hack23/cia --skill c4-architecture-documentation -a cursor` (or -a gemini-cli, github-copilot or opencode for the others). To copy it by hand, put the folder in .cursor/skills/c4-architecture-documentation, .gemini/skills/c4-architecture-documentation, .github/skills/c4-architecture-documentation and .opencode/skills/c4-architecture-documentation in your project.

What does C4 Architecture Documentation need to run?

SKILL.md names no scripts, command-line tools or credentials: C4 Architecture Documentation is instructions for the agent only.

Does C4 Architecture Documentation access the network?

SKILL.md names 2 domains. In commands or code: raw.githubusercontent.com; the agent is likely to contact it when it follows the instructions. As links in the text: c4model.com. This is read from the text; nothing was executed.

Is C4 Architecture Documentation safe to install?

Our automated static check of SKILL.md found no risky patterns, such as piping downloads into a shell, reading credential files or hidden Unicode. It is not a guarantee. Review the folder before installing.

What licence does C4 Architecture Documentation use?

C4 Architecture Documentation is published under the Apache-2.0 licence (declared in SKILL.md). It allows redistribution, so the full SKILL.md is shown on this page.

How many tokens does C4 Architecture Documentation use?

About 511 tokens (SKILL.md is roughly 2k characters). Agents keep only the skill's name and description in context until a task matches; then they load SKILL.md in full.

What are the alternatives to C4 Architecture Documentation?

Skills that share tags, products or a category with C4 Architecture Documentation: JSON Canvas (heyitsnoah/claudesidian, 2.6k stars), Archify Diagrams (tt-a1i/archify, 79k stars), Diagram Design (cathrynlavery/diagram-design, 44k stars) and Fireworks Tech Graph (tisfeng/Easydict, 15k stars). The comparison table on this page puts their stars, adoption, token cost, safety result and licence side by side.

Who maintains C4 Architecture Documentation?

Hack23 (a GitHub organization) maintains it in Hack23/cia, which has 239 GitHub stars. The repository holds 78 skills in this directory. The repository was last updated on October 6, 2026.

Source: Hack23/cia on GitHub. Facts on this page come from the repository at the commit we read; the author's words are quoted as theirs.