Diagrams.so MCP server

@diagrams-so/mcp

The Diagrams.so MCP server — generate, edit, and manage cloud architecture diagrams from any MCP client (Claude Desktop, Claude Code, Cursor). It's a thin stdio client over the public Diagrams.so API (/api/v2); every tool is one REST call.

Quick start

Needs Node ≥ 18. No API key to copy: you connect by approving in a browser.

# 1. add the server to Claude Code
claude mcp add diagrams-so -- npx -y @diagrams-so/mcp

# 2. connect this machine (a browser opens, press Approve)
npx @diagrams-so/mcp login

Restart your client, then ask: "Generate an AWS 3-tier web app diagram and show me the warnings." Run /mcp if you want to confirm all 23 tools registered first.

Using it a lot? Install once and the command gets shorter:

npm i -g @diagrams-so/mcp
diagrams-so login

The server talks to production (https://api.diagrams.so/api/v2) by default. Point it at a

local or self-hosted API with DIAGRAMSAPIBASE.

Using Claude Desktop or Cursor instead of the CLI? See Add it to your MCP client. Prefer a one-click, no-terminal install? See One-click install (MCPB).

No terminal at all (Claude Desktop)

Add the server to your client config (below) with DIAGRAMSLOGINEMAIL set to your email, then just ask for a diagram. Because the machine isn't connected yet, the first tool call emails you a one-time sign-in code and replies with a link. Open it, enter the code, press Approve, and ask again. Nothing to install or type.

Generating a diagram from Claude

login only connects the machine. It never generates anything itself, so there is no generate command to type in a terminal. You write the prompt in your assistant's normal chat box and it calls the tools for you.

MCP servers load at startup, so restart your client after adding it. Then run /mcp and confirm diagrams-so shows 23 tools.

Now just ask, in plain English:

Generate an AWS three-tier web app with an ALB, EC2 Auto Scaling and RDS Multi-AZ.

Show me the design warnings, then export it as draw.io.

Behind that one sentence the assistant calls generatediagram, then getwarnings, then export_diagram. You never name a tool or write JSON.

More things worth asking, once you have a diagram:

The warnings mention no encryption in transit. Fix that one and show me the new score.

Add a CloudFront distribution in front of the ALB.

Re-export it as SVG so I can drop it in the README.

Each reply carries the credit cost and your remaining balance. Generating, editing, fixing and re-laying-out spend credits; reading, warnings and every export are free.

The .drawio file the assistant saves opens at app.diagrams.net or in the desktop app, fully editable — it is real draw.io XML, not a picture.

Prefer not to use an assistant at all? diagrams.so/create has the same thing as a web page: type the prompt in the box. No install, no login, no MCP.

Tools (23)

Create & change (mutating)

Shortened. The full README is on GitHub.