c4-architecture

c4-architecture is a skill for Claude Code, Codex from softaworks/agent-toolkit. It costs 82 tokens per session (2,594 once invoked), scanned A, original, MIT.

A documentation tool for describing software architecture with C4 diagrams in Mermaid, a text format that renders diagrams. C4 diagrams show a system at different levels, from its users and surrounding systems to its applications and internal components.

In plain words
What is it for?
Use it to document system context, applications, databases, services, internal components, deployments, or complex request flows in Markdown files.
Why use it?
It gives teams a shared view of how a system is structured and how its parts relate, without requiring readers to study the whole codebase.

Skill for Claude CodeCodex

Install

Getting it into your agent

One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.

agentmods
npx agentmods add skills/softaworks/agent-toolkit/c4-architecture
Any agent
npx skills add softaworks/agent-toolkit --skill c4-architecture
Clone the repo
git clone --depth 1 https://github.com/softaworks/agent-toolkit

Made for: Claude Code, Codex.

Wrote this? Show the measurements

A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.

agentmods badge for c4-architecture

README.md
[![agentmods](https://agentmods.dev/badge/skills/softaworks/agent-toolkit/c4-architecture.svg)](https://agentmods.dev/skills/softaworks/agent-toolkit/c4-architecture)
Your own site
<a href="https://agentmods.dev/skills/softaworks/agent-toolkit/c4-architecture"><img src="https://agentmods.dev/badge/skills/softaworks/agent-toolkit/c4-architecture.svg" alt="Measured on agentmods" height="20"></a>
Per session 82 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 2,594 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. Scan, not verified.
Origin original No closer match found in the catalogue.
Token cost

What it costs to keep this loaded

Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.

ModelPer sessionOnce invoked
Fable 5 $0.00082 $0.02594
Opus 5 $0.00041 $0.01297
Sonnet 5 $0.00016 $0.00519
Haiku 4.5 $0.00008 $0.00259

Measured 4d ago against content hash e27b4bac48f6, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

c4-architecture scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 4d ago.

A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.

Nothing flagged

None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.

Origin

Copies of this mod

2 near-identical copies found in the catalogue:

skills/c4-architecture/SKILL.md · 296 lines

How it starts

The opening of the file, as written. The whole thing — 296 lines — stays where its author put it; the contents beside it link to each section on GitHub.

C4 Architecture Documentation

Generate software architecture documentation using C4 model diagrams in Mermaid syntax.

Workflow

  1. Understand scope - Determine which C4 level(s) are needed based on audience
  2. Analyze codebase - Explore the system to identify components, containers, and relationships
  3. Generate diagrams - Create Mermaid C4 diagrams at appropriate abstraction levels
  4. Document - Write diagrams to markdown files with explanatory context

C4 Diagram Levels

Select the appropriate level based on the documentation need:

Level Diagram Type Audience Shows When to Create
1 C4Context Everyone System + external actors Always (required)
2 C4Container Technical Apps, databases, services Always (required)
3 C4Component Developers Internal components Only if adds value
4 C4Deployment DevOps Infrastructure nodes For production systems
- C4Dynamic Technical Request flows (numbered) For complex workflows

Key Insight: "Context + Container diagrams are sufficient for most software development teams." Only create Component/Code diagrams when they genuinely add value.

Quick Start Examples

System Context (Level 1)

C4Context
  title System Context - Workout Tracker

  Person(user, "User", "Tracks workouts and exercises")
  System(app, "Workout Tracker", "Vue PWA for tracking strength and CrossFit workouts")
  System_Ext(browser, "Web Browser", "Stores data in IndexedDB")

  Rel(user, app, "Uses")
  Rel(app, browser, "Persists data to", "IndexedDB")

Container Diagram (Level 2)

C4Container
  title Container Diagram - Workout Tracker

  Person(user, "User", "Tracks workouts")

  Container_Boundary(app, "Workout Tracker PWA") {
    Container(spa, "SPA", "Vue 3, TypeScript", "Single-page application")
    Container(pinia, "State Management", "Pinia", "Manages application state")
    ContainerDb(indexeddb, "IndexedDB", "Dexie", "Local workout storage")
  }

  Rel(user, spa, "Uses")
  Rel(spa, pinia, "Reads/writes state")
  Rel(pinia, indexeddb, "Persists", "Dexie ORM")

Read the full file on GitHub · 296 lines

Files

What ships with it

4 files beside SKILL.md in the same directory: the scripts, references and assets a skill reads on demand. Not counted in the per-session cost; read them before you install if any of them is executable.

Changes

What this file has done since we first saw it

Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.

  1. 4d ago First seen · 296 lines · 82 tokens per session scan A e27b4bac48f6

Subscribe to this mod's changes

c4-architecture is a skill published in the GitHub repository softaworks/agent-toolkit (2,422 stars, last pushed 6mo ago), licensed MIT. It adds 82 tokens to every session and 2,594 once invoked, about $0.0004 per session on Opus 5. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-30.