diagrams-mcp-server

diagrams-mcp-server is a local-first MCP (Model Context Protocol) server that provides AI coding agents with structured access to a project's PlantUML and Mermaid architecture diagrams. It allows agents to 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 starter skeletons. All operations are local, with no accounts and no network calls unless explicitly opted in. The server works with any MCP-compatible client over stdio, including Claude Code, Codex, Antigravity, OpenCode, Cursor, and VS Code. It was built to keep diagrams in the project next to the code so an agent can read and check them in the same workflow. The server offers twelve tools in four groups: manage diagrams, render and share, check and compare, and draft new diagrams. The read-only drafting tools (diagrams_generate, diagrams_generate_sequence, diagrams_template, diagrams_export) never write; they return source text that the user saves with diagrams_create. Pagination and source windows are explicit and opt-in, with the server never paging or truncating on its own. Requirements include Node.js 18+ for running the server and Node.js >=20.19 for the development toolchain.