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.
npx skills add magnus919/agent-skills --skill c4-diagramminggit clone --depth 1 https://github.com/magnus919/agent-skillsWrote 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.
[](https://agentmods.dev/skills/magnus919/agent-skills/c4-diagramming)<a href="https://agentmods.dev/skills/magnus919/agent-skills/c4-diagramming"><img src="https://agentmods.dev/badge/skills/magnus919/agent-skills/c4-diagramming/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.
<a href="https://agentmods.dev/skills/magnus919/agent-skills/c4-diagramming"><img src="https://agentmods.dev/badge/skills/magnus919/agent-skills/c4-diagramming.svg" alt="Reviewed on agentmods" width="80" height="20"></a>- NVIDIA SkillSpector pass
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.
| Model | Per session | Once invoked |
|---|---|---|
| Fable 5.1 | $0.00081 | $0.01794 |
| Opus 5 | $0.00041 | $0.00897 |
| Sonnet 5 | $0.00016 | $0.00359 |
| Haiku 4.5 | $0.00008 | $0.00179 |
Grade A, and why
c4-diagramming 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 12d 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.
How it starts
The opening of the file, as written. The whole thing — 119 lines — stays where its author put it; the contents beside it link to each section on GitHub.
C4 Diagramming
C4 Model for structural architecture visualization. Produces diagrams at four zoom levels, mapped into the artifact pyramid.
C4-to-Pyramid Mapping
| C4 Level | Pyramid Layer | Path |
|---|---|---|
| Level 1: System Context | L1 (Summary) | 01-summary/system-context.md |
| Level 2: Container | L2 (Analysis) | 02-analysis/structural-views/container.md |
| Level 3: Component | L2 (Analysis) | 02-analysis/structural-views/components.md |
| Level 4: Code | L3 (Dossiers) | 03-dossiers/code-level-detail.md |
C4 is the cleanest structural fit — its four-level hierarchy maps to the three pyramid layers with almost no translation, and Levels 2-3 both resolve to separate L2 analysis files.
Communication Gate
Before choosing notation or polishing layout, state the audience and the job the reader must complete. Select one C4 level that answers that job; do not mix system context, container, component, and code claims merely to fill a canvas. Keep the abstraction level, element vocabulary, boundary treatment, and relationship meaning consistent within a view. A structurally valid C4 model can still be the wrong communication artifact if it asks the reader to infer the purpose, mixes levels, hides important paths, or overwhelms the intended reader.
Load references/technical-diagram-communication.md when creating, revising, or reviewing a diagram for a real audience. Use its review record to check narrative/read order, visual hierarchy, labels and legends, signal-to-noise, color-independent meaning, accessibility handoff, uncertainty, and review evidence. Full accessibility conformance remains owned by web-accessibility; architecture decisions remain owned by software-architecture.
Review Evidence
Record the intended audience and question, C4 level and scope, key claim, known uncertainty, target renderer, and an accessible text or tabular fallback. Review both the source model and the rendered artifact. A passing syntax/model validator proves structural validity only; it does not prove that the diagram communicates the intended claim.
What ships with it
7 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.
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.
- 12d ago First seen · 119 lines · 81 tokens per session scan A 7f064bd02553
c4-diagramming is a skill published in the GitHub repository magnus919/agent-skills (76 stars, last pushed yesterday), licensed MIT. It adds 81 tokens to every session and 1,794 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.
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