# C4 Model

> WHAT — C4 model methodology (Context, Container, Component, Code) guidance — what to draw at each level, when, and how to render C4-inspired diagrams via Mermaid (PlantUML/Structurizr optional advanced). Methodology not renderer.

- **Type:** Skill
- **Install:** `agentstack add skill-ulises-jeremias-agent-toolkit-c4-model`
- **Verified:** Yes — security-reviewed for prompt injection and unsafe behavior
- **Seller:** [ulises-jeremias](https://agentstack.voostack.com/s/ulises-jeremias)
- **Installs:** 0
- **Category:** [Developer Tools](https://agentstack.voostack.com/c/developer-tools)
- **Latest version:** 0.1.0
- **License:** MIT
- **Upstream author:** [ulises-jeremias](https://github.com/ulises-jeremias)
- **Source:** https://github.com/ulises-jeremias/agent-toolkit/tree/main/plugins/agent-toolkit-complete/.github/skills/c4-model
- **Website:** https://ulises-jeremias.github.io/agent-toolkit-archive/

## Install

```sh
agentstack add skill-ulises-jeremias-agent-toolkit-c4-model
```

Requires the [AgentStack CLI](https://agentstack.voostack.com/docs/cli). Works with Claude Code, Cursor, and any MCP-compatible agent.

## About

# C4 Model — Methodology Overlay (WHAT → HOW via Mermaid)

**Sources (2026-08-12):** Simon Brown C4 https://c4model.com/ (Context, Container, Component, Code); Structurizr DSL https://github.com/structurizr/dsl (open-source DSL, paid cloud) + `structurizr-mcp` https://github.com/cubical6/structurizr-mcp + `go-structurizr`; C4-PlantUML https://github.com/plantuml-stdlib/C4-PlantUML; overarch https://github.com/soulspace-org/overarch (PlantUML/Structurizr generation); rendering **via Mermaid** `mermaid-js/mermaid` MIT per §44.

> **Pack:** `architecture` core (`architect + ADR + TRD + threat-model + mermaid (+ C4 via mermaid)`) — `c4-model` teaches *what* to draw; `mermaid` renders it. See `docs/architecture/research-385-diagram.md` for C4 vs Mermaid vs PlantUML/Structurizr decision (Excalidraw/draw.io REJECT).

## When to use

- Need system Context / Container / Component / Code views.

## Instructions

1. **Select level:** Context (system + actors) → Container (apps/data stores) → Component (modules) → Code (classes, optional).
2. **Render via Mermaid** (C4-inspired): `flowchart TD` with `subgraph` for boundaries, e.g.:
   ```mermaid
   flowchart TD
     user([User]) --> web[Web Container]
     web --> api[API Container]
     api --> db[(Database Container)]
     subgraph System Context
       user; web; api; db
     end
   ```
3. **Advanced (optional):** For consistency checks across views, use Structurizr DSL (`structurizr-cli` + `workspace.dsl` → PlantUML/Mermaid) or C4-PlantUML (`@startuml` + `!include C4_Context.puml`); note `structurizr` CLI requires DSL file and is heavier.

## Collaboration

- `architect` defines system → `c4-model` selects C4 level → `mermaid` renders → `ADR` records decision.

## Anti-patterns

- Do not mandate Structurizr DSL for every diagram — Mermaid suffices for most.
- Do not dump PlantUML infra as separate skill — keep as optional note.

## Source & license

This open-source skill is cataloged on AgentStack and links to its original source — we do not rehost the code.

- **Author:** [ulises-jeremias](https://github.com/ulises-jeremias)
- **Source:** [ulises-jeremias/agent-toolkit](https://github.com/ulises-jeremias/agent-toolkit)
- **License:** MIT
- **Homepage:** https://ulises-jeremias.github.io/agent-toolkit-archive/

Install and usage instructions live in the source repository linked above.

## Pricing

- **Free** — Free

## Security capabilities

Automated source analysis of v0.1.0 — what this tool can access:

- **Network access:** no
- **Filesystem access:** no
- **Shell / process execution:** no
- **Environment & secrets:** no
- **Dynamic code execution:** no

*"Yes" means the capability is present in the source — more access means more to trust, not that it is unsafe.*


## Versions

- **0.1.0** — security scan: passed — Imported from the upstream source.

## Links

- Listing page: https://agentstack.voostack.com/l/skill-ulises-jeremias-agent-toolkit-c4-model
- Seller: https://agentstack.voostack.com/s/ulises-jeremias
- Browse the marketplace: https://agentstack.voostack.com/browse

---
Listed on AgentStack — the marketplace for AI agent skills and MCP servers. Every listing is security-reviewed. Creators keep 70%.