Diagrams MCP Server

diagrams-mcp-server

Technical Preview (V1 Preview, v0.7.0) — local-first MCP server for

PlantUML and Mermaid diagrams: manage, render, and share them, check them

against your codebase, and draft new ones from your code.

An MCP (Model Context Protocol) server that gives AI coding agents structured access to your project's PlantUML and Mermaid architecture diagrams. It can list, read, create, update, and delete diagrams, render and export them, check them against the codebase, diff two versions, and draft new diagrams from code or from starter skeletons — all locally, with no accounts and no network calls unless you explicitly opt in.

Works with any MCP-compatible client over stdio: Claude Code, Codex (Desktop & CLI), Antigravity (IDE, 2.0 & CLI), OpenCode (Desktop & CLI), Cursor, and VS Code. See Client setup below.

Why this exists

I built this after running into the same problem while using AI to work on software design. The diagram was in one place, the code was in another, and I kept having to paste context into the conversation. After a few rounds, it became hard to tell whether the diagram still described the project. I wanted a small local MCP server that could keep the diagram in the project, let the agent read it, and check it against the code when needed.

diagrams-mcp-server keeps diagrams in the project next to the code so an agent can read and check them in the same workflow. It uses the standard stdio MCP transport and does not require client-specific server code.

Features

Twelve tools in four groups. The read-only drafting tools (diagramsgenerate, diagramsgeneratesequence, diagramstemplate, diagramsexport) never write: they return source text and you save it yourself with diagramscreate.

Manage diagrams

Render and share

Check and compare

Draft new diagrams

Shortened. The full README is on GitHub.