UML-MCP
MCP server that renders diagrams from text or source: 46 types, including PlantUML, Mermaid, C4, BPMN and interactive maps.
- 110 ★ on the repository
- Last commit
- MIT
Extended access
Why this level
- The hosted server sees diagram text, and some types are rendered by the external Kroki service.
Install
- Works in
In your terminal, with SkillFoxx CLI
npx skillfoxx add mcp/uml-mcpDetects the agents on your machine, shows the access level and pins the version.
Other ways to install
Access and checks
How we reviewExtended accessThe tool runs code or makes network calls and only reads external data.
- The hosted server sees diagram text, and some types are rendered by the external Kroki service.
This is third-party code. Review the repository files before installing.
What it does
UML-MCP turns a plain-language description or diagram source into a finished picture inside the chat. It supports 46 types: 37 are drawn through the Kroki service (UML, Mermaid, D2, Graphviz, C4, BPMN, ERD, TikZ) and 9 are interactive. The tools: `generate_uml` returns one drawing with links, `generate_uml_image` returns a PNG for the chat, `validate_uml` checks source before rendering, `list_diagram_types` shows the catalog and `generate_uml_batch` builds several diagrams per call. In MCP Apps clients the diagram opens in a viewer with source editing and export to SVG, PNG, HTML and PDF.
Who it is for. Developers and architects who describe systems in chat and take finished diagrams into documentation.
Good fit when
- A login sequence through an API gateway has to appear in a diagram for an architecture review.
- A C4 diagram is built from a repository file set for the README.
- PlantUML or Mermaid source is validated before it lands in documentation.
- Four diagrams are built in one request and an export format is chosen.
Not a fit when
- Diagram sources hold private data that cannot go to an external service.
- Only one notation is needed and a dedicated server already covers it.
- The diagram is drawn by hand in an editor without an agent.
Example request
Draw a sequence diagram: a user signs in through an API gateway, and the gateway calls an authorization service.MCP
- Transport
- http, stdio
- Authentication
- not required
Limitations
The hosted server receives the diagram text, and 37 types additionally go to the external Kroki service, so run your own instance through Docker or Helm for private architecture. The interactive viewer works only in clients with MCP Apps support, others get PNG and SVG. Local runs need Python 3.12 to 3.15. Availability of the hosted address depends on its owner, so a self-hosted instance is safer for working processes. The result depends on the source: `validate_uml` catches syntax, but a person checks the meaning of the diagram.
How to disable. Remove the `uml-mcp` entry from the client config. If installed locally, run `uv tool uninstall uml-mcp` and stop your own containers.
FAQ
Is installation needed to start?
No. Add the hosted address `https://uml-mcp.vercel.app/mcp` to the client; a mirror on another domain exists too.
What if the client shows no viewer window?
The diagram arrives as an inline PNG and SVG with links to the file and an editable playground.
How do I run the server myself?
Run `uv tool install uml-mcp && uml-mcp setup`. The installation guide covers Docker, Helm and running from source.
Can custom diagram types be added?
Yes, through plugins. Four built-in ones (D3, stack diagrams, Archify, LLM visualizer) are on by default, and the guide explains how to write your own.
What does `validate_uml` do?
It checks source before rendering. Error messages say how to fix the problems.
Discussion
No questions or reviews yet.
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Comparison with similar tools
Cards that share the main search query, and how they differ.
| Tool | Official | Authentication | Repository stars | Main difference |
|---|---|---|---|---|
| UML-MCP (this card) | no | not required | 110 | |
| MCP Mermaid | no | not required | 649 | builds only Mermaid diagrams; UML-MCP adds PlantUML, C4, BPMN, D2 and interactive types |
| Architecture Diagram Generator | no | 7,589 | draws architecture diagrams as a skill; UML-MCP serves rendering over MCP and validates source |
README in short
One server covers 37 notations through Kroki and 9 interactive types, and MCP Apps clients can edit the diagram in a viewer.