A guide for creating technical diagrams as one self-contained HTML file, covering flows, timelines, data relationships, architecture, and other common diagram types.

Use it to create flowcharts, sequence diagrams, ER diagrams, state machines, charts, project timelines, kanban boards, and cloud architecture illustrations.

It helps turn a complex technical relationship or process into a focused diagram with a readable structure.

visualcave — Skill for Claude Code and Codex by varkart

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 varkart/visualcave --skill visualcave

Clone the repo

git clone --depth 1 https://github.com/varkart/visualcave

Made for: Claude Code, Codex.

Or install visualcave, the plugin that ships this one along with the rest of its 1 skill.

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.

README.md

[![agentmods](https://agentmods.dev/badge/skills/varkart/visualcave/visualcave/github.svg)](https://agentmods.dev/skills/varkart/visualcave/visualcave)

Your own site

<a href="https://agentmods.dev/skills/varkart/visualcave/visualcave"><img src="https://agentmods.dev/badge/skills/varkart/visualcave/visualcave/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.

Your own site · 80×15

<a href="https://agentmods.dev/skills/varkart/visualcave/visualcave"><img src="https://agentmods.dev/badge/skills/varkart/visualcave/visualcave.svg" alt="Reviewed on agentmods" width="80" height="20"></a>

Per session 78 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.

When invoked 1,216 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.

Model	Per session	Once invoked
Fable 5.1	$0.00078	$0.01216
Opus 5.5	$0.00031	$0.00486
Sonnet 5.5	$0.00016	$0.00243
Haiku 4.5	$0.00008	$0.00122

Measured 1mo ago against content hash c5e4eab55a27, method: parsed. Prices are Anthropic first-party input rates as of 2026-10-07, from the pricing page.

Security

Grade A, and why

visualcave 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 1mo ago.

The scan reads SKILL.md. This mod also ships 5 executable files (scripts/add-theme-selector.js, scripts/fix-init-pattern.js, scripts/inject-error-boundaries.js, …), listed below but not scanned — reading those needs a real analyzer, not pattern matching.

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.

SKILL.md · 85 lines

How it starts

The opening of the file, as written. The whole thing — 85 lines — stays where its author put it; the contents beside it link to each section on GitHub.

VisualCave

Output a single self-contained .html file. No markdown wrapper unless the user asks for it.

Before You Draw

1. Identify the critical path. Every good diagram has one story — the single flow or relationship the viewer must understand immediately. Name it before writing any Mermaid code. Let it govern which nodes exist and how subgraphs are grouped. Nodes that don't serve the story get cut.

2. Pick scope ruthlessly. Aim for 8–15 nodes. Beyond 20 the diagram becomes unreadable. Group related details into a single labeled node rather than expanding every sub-step.

3. Choose labels like a senior engineer preparing a conference slide — not an autogenerated dump. Node labels: 2–4 words. Edge labels: 1–3 words. Subgraph titles: a noun phrase, not a sentence.

Style rules:

Thick strokes (2px), 4px drop shadow, rounded nodes.
Warm/cool subgraph alternation: yellow → blue → green → purple → teal → orange.
Inter font for UI; JetBrains Mono for code/math labels.
Pick the right Mermaid keyword — see references/diagram-types.md.

HTML Template

Read references/template.html verbatim. Replace:

[Diagram Title] and [Subtitle] in the header
The placeholder Mermaid source inside <div class="mermaid" id="diagram-source"> with the actual diagram

Do not alter the CSS, THEMES object, or script block unless a specific feature requires it.

Colors

classDef works in graph, classDiagram, stateDiagram-v2. For other types use themeVariables.

Class	Fill	Use for
`:::yellow`	`#FFFDE7`	Users, browsers, entry points
`:::blue`	`#E3F2FD`	Services, APIs, compute
`:::green`	`#E8F5E9`	Databases, storage, success
`:::purple`	`#F3E5F5`	Auth, AI models, security
`:::teal`	`#E0F7FA`	Caching, CDN, external APIs
`:::orange`	`#FFF3E0`	Queues, events, pipelines
`:::note`	`#FFF9C4`	Annotations, callouts

Read the full file on GitHub · 85 lines

Files

What ships with it

47 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.

1mo ago First seen · 85 lines · 78 tokens per session scan A c5e4eab55a27

Subscribe to this mod's changes

visualcave is a skill published in the GitHub repository varkart/visualcave (2 stars, last pushed 1mo ago), licensed MIT. It adds 78 tokens to every session and 1,216 once invoked, about $0.0003 per session on Opus 5.5. 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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