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html-svg-diagrams

html-svg-diagrams is a skill for Claude Code from f-labs-io/agent-html-skills. It costs 103 tokens per session (3,016 once invoked), scanned A, original, MIT.

A guide to creating technical diagrams as SVG inside HTML. SVG is a web-based image format that keeps shapes, arrows, and text clear at different sizes.

In plain words
What is it for?
Creating flowcharts, sequence diagrams, state machines, data-flow diagrams, dependency graphs, and request timelines.
Why use it?
It makes relationships, sequences, states, and data flows easier to understand than plain text diagrams.

Skill for Claude Code

Written for Claude Code: ${CLAUDE_PLUGIN_ROOT} variable. Also seen: mentions Claude Code.

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 html-skills plugin — 19 skills shipped together

not rated 68repo +1 changed 1mo ago A scan Socket: passSnyk: pass 103 tokens original MIT

Good fit Creating flowcharts, sequence diagrams, state machines, data-flow diagrams, dependency graphs, and request timelines.

Compare 6 skills from other repositories ↓
View source ↗ f-labs-io/agent-html-skills
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 f-labs-io/agent-html-skills
Claude Code
/plugin install html-skills

Made for: Claude Code.

Or install html-skills, the plugin that ships this one along with the rest of its 19 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-svg-diagrams

README.md
[![agentmods](https://agentmods.dev/badge/skills/f-labs-io/agent-html-skills/html-svg-diagrams/github.svg)](https://agentmods.dev/skills/f-labs-io/agent-html-skills/html-svg-diagrams)
Your own site
<a href="https://agentmods.dev/skills/f-labs-io/agent-html-skills/html-svg-diagrams"><img src="https://agentmods.dev/badge/skills/f-labs-io/agent-html-skills/html-svg-diagrams/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.

agentmods 80×15 button for html-svg-diagrams

Your own site · 80×15
<a href="https://agentmods.dev/skills/f-labs-io/agent-html-skills/html-svg-diagrams"><img src="https://agentmods.dev/badge/skills/f-labs-io/agent-html-skills/html-svg-diagrams.svg" alt="Reviewed on agentmods" width="80" height="20"></a>
Per session 103 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 3,016 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. Third-party audits
  • Socket pass 5 Oct 2026
  • Snyk pass 5 Oct 2026
How audits are shown
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 $0.00103 $0.03016
Opus 5.5 $0.00041 $0.01206
Sonnet 5.5 $0.00021 $0.00603
Haiku 4.5 $0.00010 $0.00302

Measured 1mo ago against content hash 502b8cd00a3f, method: parsed. Prices are Anthropic first-party input rates as of 2026-10-07, from the pricing page.

Security

Grade A, and why

html-svg-diagrams 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.

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/html-skills/skills/html-svg-diagrams/SKILL.md · 172 lines

How it starts

The opening of the file, as written. The whole thing — 172 lines — stays where its author put it; the contents beside it link to each section on GitHub.

HTML SVG Diagrams & Flowcharts

ASCII diagrams in markdown are a workaround for not having SVG. With SVG inside HTML, you get real shapes, real arrows, real typography, and real positioning — for the same conceptual cost.

Use this skill any time the explanation has arrows, boxes, layers, time, or position. Most technical concepts do.

Pre-flight — run BEFORE writing the artifact

Invoke html-skills:html-skills-listen (Skill tool) first; it is idempotent. If it returns a URL, inject it verbatim as window.__CLAUDE_SUBMIT_URL__ in the HTML you are about to write, ?t= query string included (a local, single-session loopback handshake — not a credential). If it reported web/sandbox mode, leave that line out; submitToClaude then falls back to clipboard mode.

When to use this skill

  • "Diagram / illustrate / visualize / draw X"
  • "Show me how the [request, data, message] flows"
  • "Sketch the [architecture, state machine, sequence]"
  • "Map the [dependencies, components, boundaries]"
  • Any explanation where the prose would lean heavily on words like "first… then… meanwhile… eventually" — those are sequence diagrams begging to be drawn

When NOT to use this skill

This is the general fallback. When the prompt names a specific subject, hand off to the specialised skill that knows the conventions:

  • System architecture, microservices, deployment topology → html-architecture-diagrams (service maps, ownership boundaries, on-call use)
  • Database schema, ERD, table relationships → html-erd-explorer (PK/FK/cardinality, migrations)
  • Time axis, roadmap, Gantt, incident timeline → html-timeline-roadmap (lanes, dependencies, "today" marker)

Use this skill when the diagram is conceptual or general-purpose (flowchart, state machine, sequence, dependency graph between abstract things). The specialised skills win when the subject is a real system, schema, or schedule.

Output requirements

SVG inline using real <svg> and <g> elements. Use viewBox so the diagram scales without re-layout. Pair every diagram with a short prose explanation underneath — the diagram alone is rarely enough.

Read the full file on GitHub · 172 lines

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. 1mo ago Changed · +1 lines 502b8cd00a3f
  2. 2mo ago Changed · +14 lines a7795faa16bd
  3. 2mo ago First seen · 157 lines · 103 tokens per session scan A 606dad1e44b2

Subscribe to this mod's changes

html-svg-diagrams is a skill published in the GitHub repository f-labs-io/agent-html-skills (68 stars, last pushed 1mo ago), licensed MIT. It adds 103 tokens to every session and 3,016 once invoked, about $0.0004 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 2026-08-30.

Design and UXFrontend
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