uml-mcp-diagrams

uml-mcp-diagrams is a skill for Claude Code, Codex from antoinebou12/uml-mcp. It costs 83 tokens per session (3,284 once invoked), scanned A, original, MIT.

A diagram-making tool that turns text written in formats such as PlantUML, Mermaid, or D2 into diagrams and shareable Kroki links. It can also check whether diagram text is valid.

In plain words
What is it for?
Use it to create, validate, and share software diagrams such as system designs, flowcharts, and UML diagrams.
Why use it?
It removes the need to manually render diagrams or guess whether their source text will work.

Skill for Claude CodeCodex

Written for no agent in particular: nothing here depends on one. Also seen: mentions Claude Code.

Good fit Use it to create, validate, and share software diagrams such as system designs, flowcharts, and UML diagrams.

Compare 6 skills from other repositories ↓
Install with agentmods
npx agentmods add skills/antoinebou12/uml-mcp/uml-mcp-diagrams
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 antoinebou12/uml-mcp --skill uml-mcp-diagrams
Clone the repo
git clone --depth 1 https://github.com/antoinebou12/uml-mcp

Made for: Claude Code, Codex.

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 uml-mcp-diagrams

README.md
[![agentmods](https://agentmods.dev/badge/skills/antoinebou12/uml-mcp/uml-mcp-diagrams/github.svg)](https://agentmods.dev/skills/antoinebou12/uml-mcp/uml-mcp-diagrams)
Your own site
<a href="https://agentmods.dev/skills/antoinebou12/uml-mcp/uml-mcp-diagrams"><img src="https://agentmods.dev/badge/skills/antoinebou12/uml-mcp/uml-mcp-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 uml-mcp-diagrams

Your own site · 80×15
<a href="https://agentmods.dev/skills/antoinebou12/uml-mcp/uml-mcp-diagrams"><img src="https://agentmods.dev/badge/skills/antoinebou12/uml-mcp/uml-mcp-diagrams.svg" alt="Reviewed on agentmods" width="80" height="20"></a>
Per session 83 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 3,284 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
  • NVIDIA SkillSpector warn 7 Sept 2026
SkillSpector: 1 finding, up to medium

These are SkillSpector’s own severities. On a checked sample its high-severity flags on skills were ~96% false positives — a documented command, a public API, a “never do X” rule — so we show them as a caution to read, not a verdict. Why →

  • medium Agent Snooping · line 10
    Skill enumerates or reads other installed skills. Access to other skills' SKILL.md files or the skills directory reveals prompt instructions, capabilities, and secrets that should be invisible to peer skills.
    Fix: Remove all code or instructions that list or read other skills' files or directories. Skills should operate independently; cross-skill access is a privilege escalation.
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 $0.00083 $0.03284
Opus 5 $0.00042 $0.01642
Sonnet 5 $0.00017 $0.00657
Haiku 4.5 $0.00008 $0.00328

Measured 7d ago against content hash 12e5085387f5, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-12, from the pricing page.

Security

Grade A, and why

uml-mcp-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 7d 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.

.skill/skills/uml-mcp-diagrams/SKILL.md · 160 lines

How it starts

The opening of the file, as written. The whole thing — 160 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Maintainers: Keep tool tables and output_dir wording aligned with the Smithery bundle uml-skill/SKILL.md (diagramming-uml) and the Claude Code plugin skill plugins/uml-mcp/skills/uml-diagrams/SKILL.md when you edit any of them.

uml-mcp diagram workflow

Goal

Turn the user’s intent into valid diagram_type + source code, call generate_uml (or generate_uml_image for chat-visible pictures), and surface the url (and playground when present). Prefer URL-first output (omit output_dir / use null) unless the user explicitly asks to save a file. When the user asks to show the diagram in chat, prefer generate_uml_image with output_format: png.

Positive patterns (do)

  • Confirm types first when unsure: read uml://types / uml://formats or call list_diagram_types before generate_uml. Catalog includes ~37 Kroki-backed types (including goat, umlet).
  • Match diagram_type to the language of code (e.g. Mermaid body → mermaid; PlantUML with @startumlplantuml or the specific Kroki PlantUML subtype if applicable).
  • Use validate_uml before an expensive retry loop or when the user pastes untrusted LLM output. Prefer strict: true for Mermaid sequence diagrams.
  • Mermaid sequence: put each statement on its own line. Do not pack sequenceDiagram; participant A; A->>B: hi on one line — strict validation rejects that; flowcharts may still use end-of-statement ;.
  • Return url, playground, and a short copy of code every time. Always format them as markdown links in the chat reply (see reply template). Never omit Playground when the tool returned it.
  • For inline chat images, call generate_uml_image (png default). It fetches bytes even on hosted Vercel when MCP_URL_ONLY is on. generate_uml with output_format: png/jpeg also force-fetches. Tool text includes ![diagram](url), URL:, and Playground: for clients that do not attach ImageContent.
  • When an LLM produces the diagram text first, prefer fenced or raw source that downstream tools accept; strip ``` fences from pasted input when needed, but still prefer clean DSL without prose inside the diagram.

Read the full file on GitHub · 160 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. 7d ago Changed · +44 lines · +14 tokens per session 12e5085387f5
  2. 12d ago First seen · 116 lines · 69 tokens per session scan A be872759dbb8

Subscribe to this mod's changes

uml-mcp-diagrams is a skill published in the GitHub repository antoinebou12/uml-mcp (99 stars, last pushed yesterday), licensed MIT. It adds 83 tokens to every session and 3,284 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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