c4-diagram-generator

c4-diagram-generator is an agent for Claude Code from devfullcycle/claude-mkt-place. It costs 0 tokens per session (8,159 once invoked), scanned A, original, no licence file.

An agent that generates C4 diagrams in PlantUML from Feature Design Documents and similar technical specifications. C4 shows software architecture from broad system views down to detailed code views, and PlantUML is a text format for diagrams.

In plain words
What is it for?
Use it to generate System Context, Container, Component, and Code-level diagrams for a planned feature or system.
Why use it?
It turns an FDD into structured architecture views without requiring manual diagram drawing.

Agent for Claude Code

Written for Claude Code: shipped in a Claude Code plugin. Also seen: model in frontmatter.

Part of the diagrams-generator plugin — 2 commands, 2 agents shipped together

Good fit Use it to generate System Context, Container, Component, and Code-level diagrams for a planned feature or system.

Compare 6 agents from other repositories ↓
Install with agentmods
npx agentmods add agents/devfullcycle/claude-mkt-place/c4-diagram-generator
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.

Clone the repo
git clone --depth 1 https://github.com/devfullcycle/claude-mkt-place

Made for: Claude Code.

Or install diagrams-generator, the plugin that ships this one along with the rest of its 2 commands, 2 agents.

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-generator

README.md
[![agentmods](https://agentmods.dev/badge/agents/devfullcycle/claude-mkt-place/c4-diagram-generator.svg)](https://agentmods.dev/agents/devfullcycle/claude-mkt-place/c4-diagram-generator)
Your own site
<a href="https://agentmods.dev/agents/devfullcycle/claude-mkt-place/c4-diagram-generator"><img src="https://agentmods.dev/badge/agents/devfullcycle/claude-mkt-place/c4-diagram-generator.svg" alt="Measured on agentmods" height="20"></a>
Per session 0 Only the description is in the session, so the agent can decide to use it. The body loads when it is invoked.
When invoked 8,159 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 unknown 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 $0.00000 $0.08159
Opus 5 $0.00000 $0.04079
Sonnet 5 $0.00000 $0.01632
Haiku 4.5 $0.00000 $0.00816

Measured 8d ago against content hash d89f737d78f4, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-07, from the pricing page.

Security

Grade A, and why

c4-diagram-generator 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 8d 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.

plugins/diagrams-generator/agents/c4-diagram-generator.md · 783 lines

The source is not reproduced here

No licence file

A repository with no LICENSE is all rights reserved by default, so the body is not copied here. The metadata, the measurements and the link are.

Read it on GitHub

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. 8d ago First seen · 783 lines · 0 tokens per session scan A d89f737d78f4

Subscribe to this mod's changes

c4-diagram-generator is an agent published in the GitHub repository devfullcycle/claude-mkt-place (61 stars, last pushed 7mo ago), with no licence file. It costs nothing until one of its globs matches a file; then it loads 8,159 tokens. 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.

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