c4-diagram

c4-diagram is a skill for Claude Code, Codex from vijayjoshi24/ea-agent-skills. It costs 133 tokens per session (716 once invoked), scanned A, original, MIT.

A tool for creating C4 architecture diagrams: pictures that show a system and its users, deployable parts, and internal building blocks at different levels of detail. It produces interactive SVG images, a web-friendly vector format.

In plain words
What is it for?
Use it to document system context, services and other deployable units, or components inside one service.
Why use it?
It helps different audiences understand the same system without forcing everyone to read source code or overly detailed diagrams. The level can match executives, architects, or engineers.

Skill for Claude CodeCodex

Written for no agent in particular: nothing here depends on one.

Good fit Use it to document system context, services and other deployable units, or components inside one service.

Compare 6 skills from other repositories ↓
Install with agentmods
npx agentmods add skills/vijayjoshi24/ea-agent-skills/c4-diagram
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.

Any agent
npx skills add vijayjoshi24/ea-agent-skills --skill c4-diagram
Clone the repo
git clone --depth 1 https://github.com/vijayjoshi24/ea-agent-skills

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-diagram

README.md
[![agentmods](https://agentmods.dev/badge/skills/vijayjoshi24/ea-agent-skills/c4-diagram/github.svg)](https://agentmods.dev/skills/vijayjoshi24/ea-agent-skills/c4-diagram)
Your own site
<a href="https://agentmods.dev/skills/vijayjoshi24/ea-agent-skills/c4-diagram"><img src="https://agentmods.dev/badge/skills/vijayjoshi24/ea-agent-skills/c4-diagram/github.svg" alt="Measured on agentmods" height="20"></a>

Or the 80×15 button, for a site that already has a row of RSS and ATOM ones. Only the verdict fits; the numbers stay here.

agentmods 80×15 button for c4-diagram

Your own site · 80×15
<a href="https://agentmods.dev/skills/vijayjoshi24/ea-agent-skills/c4-diagram"><img src="https://agentmods.dev/badge/skills/vijayjoshi24/ea-agent-skills/c4-diagram.svg" alt="Reviewed on agentmods" width="80" height="20"></a>
Per session 133 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 716 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. A grade says what 26 rules found in the file — not that it is safe.
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 5.1 $0.00133 $0.00716
Opus 5 $0.00067 $0.00358
Sonnet 5 $0.00027 $0.00143
Haiku 4.5 $0.00013 $0.00072

Measured 11d ago against content hash 357aa1dc2541, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-11, from the pricing page.

Security

Grade A, and why

c4-diagram 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 11d 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.

skills/c4-diagram/SKILL.md · 89 lines

How it starts

The opening of the file, as written. The whole thing — 89 lines — stays where its author put it; the contents beside it link to each section on GitHub.

C4 Diagram

Generate interactive C4 model diagrams at the right zoom level for your audience. Read references/notation.md before rendering any diagram.


The Four Levels

Level Audience Shows
1 — Context Business, executives The system + its users + external systems
2 — Container Architects, tech leads Deployable units inside the system
3 — Component Engineering teams Structural building blocks inside one container
4 — Code Developers Class/interface level — skip unless explicitly requested

Step 1 — Determine Level and Extract Elements

If the user hasn't specified a level, default to Context first.

Extract from the user's description:

Context: system in scope · people/actors · external systems · relationships
Container: containers (with technology) · external systems they call · relationships with protocols
Component: which container to zoom into · components (with pattern/technology) · internal + external relationships

State any assumptions you make (e.g. "Assumed: auth is delegated to the API Gateway").


Step 2 — Render the Diagram

Use the show_widget visualiser. Follow references/notation.md exactly for:

  • Shapes and colours per element type
  • Label format: name · [type] · description (one sentence)
  • Relationship arrows: one direction, labelled with intent + technology
  • Title: {Level} Diagram — {System Name}
  • Legend in bottom-right corner

Make every element clickable to drill down:

  • Container in Context → sendPrompt('Draw the Container diagram for {system}')
  • Container in Container → sendPrompt('Draw the Component diagram for {container}')
  • External system → sendPrompt('Explain the {system} integration')

Max 10 elements per diagram. If more exist, scope to the most relevant and note omissions.


Step 3 — Quality Gate

Before delivering, verify:

  • Title present
  • Every element: name + [type] + description
  • Every relationship: directional arrow + intent label
  • External systems visually distinct (grey)
  • People distinct from systems
  • Legend present
  • ≤10 elements

Read the full file on GitHub · 89 lines

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. 11d ago First seen · 89 lines · 133 tokens per session scan A 357aa1dc2541

Subscribe to this mod's changes

c4-diagram is a skill published in the GitHub repository vijayjoshi24/ea-agent-skills (5 stars, last pushed 4mo ago), licensed MIT. It adds 133 tokens to every session and 716 once invoked, about $0.0007 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 2026-08-31.

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