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Agent skill

Uml Diagrams

by antoinebou12 in antoinebou12/uml-mcp

Create and validate diagrams with the uml-mcp MCP server (generateuml, generateumlimage, validateuml, listdiagramtypes, generateumlbatch).

MITAuto-check passedDevelopment

Install Uml Diagrams

skills CLI
$ npx skills add antoinebou12/uml-mcp --skill uml-diagrams -a claude-code

Project install by default; add -g for ~/.claude/skills/.

GitHub CLI
$ gh skill install antoinebou12/uml-mcp uml-diagrams --agent claude-code

Project scope by default; add --scope user for a personal install. Needs GitHub CLI 2.90.0 or later (public preview).

Manual copy
$ git clone --depth 1 https://github.com/antoinebou12/uml-mcp.git skills-src && mkdir -p .claude/skills && cp -r skills-src/plugins/uml-mcp/skills/uml-diagrams .claude/skills/uml-diagrams && rm -rf skills-src

Use ~/.claude/skills/ instead of .claude/skills for a personal install. The folder must contain SKILL.md.

Claude Code skills documentation · loads skills from .claude/skills/

Facts

Skill name
uml-diagrams
GitHub stars
105
Token cost
~1.3k tokens
SKILL.md length
509 words
Files
1
Skills in repo
7
Repo updated
First seen
Licence
MIT

At a glance

Create and validate diagrams with the uml-mcp MCP server (generateuml, generateumlimage, validateuml, listdiagramtypes, generateumlbatch).

  • Works in 3 steps: Read uml://types / uml://capabilities… → Use uml://templates, uml://examples, or… → Optional: validate_uml with strict: true…
  • Inline chat images
  • SKILL.md covers Goal, Do, Do not and Before generating, plus 6 more sections
  • Instructions only: no scripts, shell commands, URLs or credentials in SKILL.md

What it does

Uml Diagrams is an agent skill from antoinebou12/uml-mcp. Create and validate diagrams with the uml-mcp MCP server (generateuml, generateumlimage, validateuml, listdiagramtypes, generateumlbatch). Use for UML, Mermaid, D2, Graphviz, Kroki URLs, inline chat images, goat/umlet, or diagramtype questions.

Its SKILL.md is about 1.3k tokens, which your agent loads only when the skill is triggered. It is a single SKILL.md file with no bundled scripts.

It sits in Development, covering Diagrams. It works with Model Context Protocol and Mermaid. The repository describes itself as: UML-MCP Server is a UML diagram generation tool based on MCP (Model Context Protocol), which can help users generate various types of UML diagrams through natural language…. The licence is MIT.

When your agent uses it

  • Inline chat images
  • Diagramtype questions

Example prompts

  • “/uml-diagrams”

Workflow steps

3 steps, taken from the first numbered list in SKILL.md.

  1. Read uml://types / uml://capabilities when the type is ambiguous.
  2. Use uml://templates, uml://examples, or uml://recipes for starters.
  3. Optional: validate_uml with strict: true for stricter Mermaid/D2 checks.

What it can do on your machine

Read from SKILL.md and the folder at commit b4413c7. It shows what the files ask for, not the result of running them.

  • Tool permissions

    Pre-approves nothing: there is no allowed-tools line, so your agent's usual permission prompts apply.

    From allowed-tools in the SKILL.md frontmatter.

  • Runs code

    No scripts in the folder and no shell commands in SKILL.md (its code samples are markdown).

    From the folder's file list and the shell code blocks in SKILL.md.

  • Network

    Links to these hosts (documentation or services it may open):

    • github.com

    From URLs in SKILL.md, links to its own repository left out.

  • Credentials

    Names no API keys, tokens, secrets or passwords.

    From names ending in _API_KEY, _TOKEN, _SECRET, _KEY or _PASSWORD in SKILL.md.

Context cost

Uml Diagrams loads about 1.3k tokens when it runs. Until then it costs about 67 tokens; SKILL.md has 509 words of instructions outside code blocks.

Always · name and description, kept in context so the agent knows when to use it
~67
When it runs · the whole SKILL.md, loaded when a task matches
~1.3k

Estimates: characters ÷ 4, the usual rule of thumb; real counts depend on the model's tokenizer. Scripts and assets cost tokens only if the agent reads them.

Safety

Auto-check passed

The automated check found no risky patterns in SKILL.md.

Automated static check — not a guarantee. Review scripts before installing. It scans the text of SKILL.md for risky patterns (piping downloads into a shell, reading credential files, hidden Unicode, destructive commands); files beside SKILL.md are not scanned.

SKILL.md

The full file from antoinebou12/uml-mcp at commit b4413c7, republished under its MIT licence (© antoinebou12). 509 words, ~1,282 tokens.

Download SKILL.mdSave it as .claude/skills/uml-diagrams/SKILL.md (or your agent's skills folder).
name
uml-diagrams
description
Create and validate diagrams with the uml-mcp MCP server (generate_uml, generate_uml_image, validate_uml, list_diagram_types, generate_uml_batch). Use for UML, Mermaid, D2, Graphviz, Kroki URLs, inline chat images, goat/umlet, or diagram_type questions.

Maintainers: Canonical long-form copy also lives in .skill/skills/uml-mcp-diagrams/SKILL.md. Keep tool tables and output_dir wording aligned with the Smithery bundle uml-skill.

UML-MCP in Claude Code

Goal

Produce valid diagram_type and DSL code, call generate_uml (or generate_uml_image to show a picture in chat), and give the user the url (and playground when present). Prefer URL-first output: omit output_dir / use null unless the user wants files on disk (local stdio only).

Do

  • If diagram_type is unclear, use list_diagram_types or read uml://types / uml://formats before generate_uml (~37 types, including goat and umlet).
  • Match diagram_type to the language of code (e.g. Mermaid body → mermaid; @startuml → plantuml or the specific Kroki PlantUML subtype when applicable).
  • Use validate_uml before heavy retry loops or on pasted diagram source; use strict: true for Mermaid sequences.
  • Mermaid sequenceDiagram: one statement per line — do not pack with ; on a single line.
  • For inline chat images, call generate_uml_image with png (fetches bytes even when hosted MCP_URL_ONLY is on). generate_uml with png/jpeg also force-fetches; SVG replies include a markdown image URL in the tool text.
  • Return the url, playground (as a markdown link when present), and a short copy of code.
  • Do not link local output/*.png paths in chat; use MCP image content or the HTTPS URL.

Do not

  • Invent diagram_type or output_format; confirm from uml://types / uml://formats or list_diagram_types.
  • Put prose inside code—only valid diagram DSL.
  • Set output_dir unless the user asked for saved files (not applicable to the default HTTP deployment).
  • Pack Mermaid sequence statements with ; on one physical line.
  • Omit playground when the tool returned it — always surface it as Playground: open editor.

Before generating

  1. Read uml://types / uml://capabilities when the type is ambiguous.
  2. Use uml://templates, uml://examples, or uml://recipes for starters.
  3. Optional: validate_uml with strict: true for stricter Mermaid/D2 checks.
Show full SKILL.md (219 more words)Show less

Tools and resources

  • Tools: generate_uml, generate_uml_image, validate_uml, list_diagram_types, generate_uml_batch
  • Resources: uml://types, uml://formats, uml://templates, uml://examples, uml://capabilities, uml://recipes, uml://server-info, uml://workflow, plus URIs from resources/list

Prompts (when exposed): uml_diagram, uml_diagram_with_thinking, class_diagram, sequence_diagram, activity_diagram, usecase_diagram, mermaid_sequence_api, mermaid_gantt, bpmn_process_guide, c4_model, wireviz_harness, bpmn_executable_process, convert_class_to_mermaid, algorithm_explainer, paper_concept_diagram.

generate_uml inputs

FieldNotes
diagram_typeRequired; must match server-supported keys.
codeRequired; DSL only.
output_dirOmit for HTTP MCP (URL + base64 when not URL-only).
output_formatOften svg; use png for chat ImageContent. Check uml://formats.
themePlantUML types only.
scaleSVG only.

generate_uml_image

Same diagram fields as generate_uml; default png. Use when the user wants the diagram visible in chat. On Vercel / MCP_URL_ONLY, this tool still force-fetches image bytes for MCP ImageContent.

generate_uml_batch

Bounded concurrency (MCP_BATCH_CONCURRENCY, default 4). Mermaid-majority batches are capped at 2 workers on the server. Recover failed Mermaid items with solo generate_uml.

After generation

Present this shape every time:

markdown
![diagram](<url>)

- **URL:** <url>
- **Playground:** <playground>

\`\`\`mermaid
<code>
\`\`\`

Copy url / playground only from the MCP tool result. On error, fix DSL or types and retry or run validate_uml. Smoke prompt: tests/prompts/chatgpt_mcp_smoke_test.md.

Intent → type hints

IntentTypical diagram_type
Classes / associationsclass or Mermaid classDiagram
Lifelines / messagessequence or Mermaid sequence
Flow / BPMNactivity, bpmn, or Mermaid flowchart
Quick chartsmermaid
Declarative layoutd2
ASCII art → SVGgoat or svgbob
UMLet UXFumlet

When several fit, prefer what the user named; otherwise prefer the clearest match from uml://types.

© antoinebou12, MIT. Rendered from Markdown: HTML in the file is shown as text, images as links, and headings moved down two levels. Raw file

Files

Just SKILL.md in plugins/uml-mcp/skills/uml-diagrams of antoinebou12/uml-mcp.

Open the folder on GitHubat commit b4413c7

Compare with similar skills

Uml Diagrams next to the 5 skills that share the most tags, products or categories with it. Stars are the repository's; “used in” counts other GitHub owners with a copy.

Uml Diagrams compared with similar skills
SkillStarsUsed inTokensAuto-checkLicenceRepo updated
Uml Diagrams this skillantoinebou12/uml-mcp105—~1.3kAutomated safety check: PassMIT
Excalidraw Skillyctimlin/mcp_excalidraw2.5k—~4.6kAutomated safety check: PassMIT
GitDiagram Repository Overviewahmedkhaleel2004/gitdiagram18k—~427Automated safety check: PassMIT
Drawiobahayonghang/drawio-skills287—~4.1kAutomated safety check: NotesMIT
Mermaid Diagramsveelenga/claude-mermaid216—~1.3kAutomated safety check: PassMIT
Excalidraw Canvas Toolkitlingzhi227/agent-research-skills390—~3.8kAutomated safety check: PassNone

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Works with

Categories

Questions about Uml Diagrams

What does Uml Diagrams do?

Create and validate diagrams with the uml-mcp MCP server (generateuml, generateumlimage, validateuml, listdiagramtypes, generateumlbatch). Uml Diagrams is an agent skill from antoinebou12/uml-mcp. Create and validate diagrams with the uml-mcp MCP server (generateuml, generateumlimage, validateuml, listdiagramtypes, generateumlbatch).

When should I use Uml Diagrams?

Uml Diagrams fits situations like: inline chat images; diagramtype questions.

How do I install Uml Diagrams in Claude Code?

Run `npx skills add antoinebou12/uml-mcp --skill uml-diagrams -a claude-code`. Or copy the skill folder (plugins/uml-mcp/skills/uml-diagrams in antoinebou12/uml-mcp) into .claude/skills/uml-diagrams in your project. Claude Code loads it when a task matches its description.

How do I install Uml Diagrams in Codex?

Run `npx skills add antoinebou12/uml-mcp --skill uml-diagrams -a codex`. Or copy the skill folder (plugins/uml-mcp/skills/uml-diagrams in antoinebou12/uml-mcp) into .agents/skills/uml-diagrams in your project. Codex loads it when a task matches its description.

Can I use Uml Diagrams in Cursor, Gemini CLI or GitHub Copilot?

Cursor, Gemini CLI, GitHub Copilot and OpenCode also load SKILL.md folders. With the skills CLI, run `npx skills add antoinebou12/uml-mcp --skill uml-diagrams -a cursor` (or -a gemini-cli, github-copilot or opencode for the others). To copy it by hand, put the folder in .cursor/skills/uml-diagrams, .gemini/skills/uml-diagrams, .github/skills/uml-diagrams and .opencode/skills/uml-diagrams in your project.

What does Uml Diagrams need to run?

SKILL.md names no scripts, command-line tools or credentials: Uml Diagrams is instructions for the agent only.

Does Uml Diagrams access the network?

SKILL.md names 1 domain. As links in the text: github.com. This is read from the text; nothing was executed.

Is Uml Diagrams safe to install?

Our automated static check of SKILL.md found no risky patterns, such as piping downloads into a shell, reading credential files or hidden Unicode. It is not a guarantee. Review the folder before installing.

What licence does Uml Diagrams use?

Uml Diagrams is published under the MIT licence (the repository's licence). It allows redistribution, so the full SKILL.md is shown on this page.

How many tokens does Uml Diagrams use?

About 1.3k tokens (SKILL.md is roughly 5.1k characters). Agents keep only the skill's name and description in context until a task matches; then they load SKILL.md in full.

What are the alternatives to Uml Diagrams?

Skills that share tags, products or a category with Uml Diagrams: Excalidraw Skill (yctimlin/mcp_excalidraw, 2.5k stars), GitDiagram Repository Overview (ahmedkhaleel2004/gitdiagram, 18k stars), Drawio (bahayonghang/drawio-skills, 287 stars) and Mermaid Diagrams (veelenga/claude-mermaid, 216 stars). The comparison table on this page puts their stars, adoption, token cost, safety result and licence side by side.

Who maintains Uml Diagrams?

antoinebou12 (a GitHub user) maintains it in antoinebou12/uml-mcp, which has 105 GitHub stars. The repository holds 7 skills in this directory. The repository was last updated on October 11, 2026.

Source: antoinebou12/uml-mcp on GitHub. Facts on this page come from the repository at the commit we read; the author's words are quoted as theirs.