html-diagram

html-diagram is a skill for Claude Code from atman-33/workhub. It costs 93 tokens per session (1,357 once invoked), scanned A, original, MIT.

A skill for creating a self-contained HTML file containing an SVG diagram. SVG is a web format for drawing shapes and lines that stays sharp when resized.

In plain words
What is it for?
Use it to make flowcharts, sequence diagrams, architecture diagrams, timelines, or trees when a visual explanation is clearer than text.
Why use it?
It helps turn system explanations, processes, timelines, and other relationships into a readable diagram without external image files.

Skill for Claude Code

Written for Claude Code: allowed-tools in frontmatter.

Runs only inside its plugin — its command needs a path that Claude Code sets for a plugin’s own hooks and for nothing else. Install the plugin, not this.

Part of the visuals plugin — 4 skills shipped together

Good fit Use it to make flowcharts, sequence diagrams, architecture diagrams, timelines, or trees when a visual explanation is clearer than text.

Compare 6 skills from other repositories ↓
Install

Getting it into your agent

This one installs as part of its plugin. Adding the marketplace and installing the plugin brings it with everything else the plugin ships.

Claude Code
/plugin marketplace add atman-33/workhub
Claude Code
/plugin install visuals

Made for: Claude Code.

Or install visuals, the plugin that ships this one along with the rest of its 4 skills.

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 html-diagram

README.md
[![agentmods](https://agentmods.dev/badge/skills/atman-33/workhub/html-diagram.svg)](https://agentmods.dev/skills/atman-33/workhub/html-diagram)
Your own site
<a href="https://agentmods.dev/skills/atman-33/workhub/html-diagram"><img src="https://agentmods.dev/badge/skills/atman-33/workhub/html-diagram.svg" alt="Measured on agentmods" height="20"></a>
Per session 93 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 1,357 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 $0.00093 $0.01357
Opus 5 $0.00046 $0.00678
Sonnet 5 $0.00019 $0.00271
Haiku 4.5 $0.00009 $0.00136

Measured 2d ago against content hash cc420ae27182, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-07, from the pricing page.

Security

Grade A, and why

html-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 2d ago.

The scan reads SKILL.md. This mod also ships 1 executable file (scripts/self-check.mjs), 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.

plugins/visuals/skills/html-diagram/SKILL.md · 151 lines

How it starts

The opening of the file, as written. The whole thing — 151 lines — stays where its author put it; the contents beside it link to each section on GitHub.

HTML diagram

One .html file, inline SVG, embedded CSS, no external images. It opens anywhere and travels as an attachment.

Source: diagram-design. See the plugin's NOTICE.md.

The one rule that governs the rest

The highest-quality move is usually deletion.

  • Every node is a distinct idea. Two nodes that always travel together are one node.
  • Every connector carries information. If the relationship is obvious from the layout, remove the line.
  • The accent colour is editorial, not a flag. One or two focal nodes. Accenting five erases the signal.
  • The diagram is not finished when everything is on it. It is finished when nothing can come off.

Target density 4 out of 10: technically complete, not so dense it needs its own guide. Above nine nodes it is probably two diagrams.

Before drawing

Ask yourself: would the reader learn more from this than from a well-written paragraph? If not, write the paragraph.

Do not draw for a list of things (use a table), a simple before/after (a table), or a single shape (write the sentence).

Then say in one short message what you are about to draw — the type, and anything the complexity budget will force out — so the user can redirect before you spend the render. Skip that pause only when the request already pins the type and content exactly.

Choose the type

Read references/diagram-types.md and pick one. Eight types cover almost everything:

Showing Type
Decision logic with branches Flowchart
Time-ordered messages between actors Sequence
Components and their connections Architecture
Events positioned in time Timeline
Parent to children Tree
A cross-functional process with handoffs Swimlane
Two-axis positioning or prioritisation Quadrant
A reinforcing cycle where the last step feeds the first Loop

If two seem to fit, pick the dominant axis. If a three-column table says the same thing, use the table.

Read the full file on GitHub · 151 lines

Files

What ships with it

3 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.

  1. 2d ago First seen · 151 lines · 93 tokens per session scan A cc420ae27182

Subscribe to this mod's changes

html-diagram is a skill published in the GitHub repository atman-33/workhub (2 stars, last pushed 2d ago), licensed MIT. It adds 93 tokens to every session and 1,357 once invoked, about $0.0005 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 2026-09-05.

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