@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 DIAGRAMS_API_BASE.

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).

<details> <summary>No terminal at all (Claude Desktop)</summary>

Add the server to your client config (below), then just ask for a diagram. Because the machine isn't connected yet, the first tool call replies with a link. Open it, press Approve, and ask again. Nothing to install or type. </details>

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.

Client	Where you type the prompt
Claude Code	the terminal chat, same place you ask anything else
Claude Desktop	the normal message box
Cursor	the chat or composer panel

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 generate_diagram, then get_warnings, 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)

Tool	What it does	Cost
generate_diagram	Create a diagram from a prompt → id + draw.io XML + warnings + score	credits
edit_diagram	Apply a natural-language change (new version)	credits
fix_warning	Resolve one Well-Architected warning	credits
relayout_diagram	AI re-arrange the layout (async; first 2/diagram free, then confirm)	credits*
import_diagram	Import existing draw.io XML as a new diagram	free
update_diagram	Rename / change visibility / replace XML	free
revert_diagram	Revert to an earlier version	free
delete_diagram	Soft-delete a diagram (destructive)	free
fork_template	Copy a public/library diagram into your account (private)	free

Read (free)

Tool	What it does
get_diagram	Fetch a diagram's XML + score
list_diagrams	List your diagrams (cursor-paginated)
get_warnings	Well-Architected findings for a diagram
export_diagram	Raw drawio or svg file (SVG is a paid feature)
list_versions	Version history (with is_current)
get_version	A specific version's XML + score
get_relayout_status	Poll an async re-layout job
search_gallery	Search public community + curated library diagrams
enhance_prompt	Turn a rough idea into a detailed prompt
clarify_prompt	Get clarifying questions for a vague prompt
get_usage	Plan + credits + cost estimates
get_usage_history	Itemized credit ledger per task (action, credits, diagram, surface) with filters + a live session tally
whoami	Account, plan, scopes, live/test mode
list_capabilities	Valid diagram types / providers / export formats

Reads and exports are free; generate / edit / fix / relayout cost credits, and delete is destructive. relayout asks for confirm=true before it charges.

CLI

Commands

Installing the package puts diagrams-so on your PATH. The longer diagrams-so-mcp name still works, and npx @diagrams-so/mcp <command> works without installing anything.

npm i -g @diagrams-so/mcp

diagrams-so login          # connect this machine (a browser opens, press Approve)
diagrams-so whoami         # which account is this machine connected as
diagrams-so logout         # remove the local credential
diagrams-so install        # print client config to paste

Environment

Var	Required	Default
DIAGRAMS_API_KEY	❌	— (CI and headless only; login is the normal path)
DIAGRAMS_API_BASE	❌	https://api.diagrams.so/api/v2 (production; override for local/self-hosted)
DIAGRAMS_API_TIMEOUT_MS	❌	450000 (per-request safety-net; sits above the API's full server-side timeout ladder)
DIAGRAMS_BROWSER	❌	— (login opens your default browser; set e.g. Google Chrome when your Diagrams.so session lives in a non-default browser)
DIAGRAMS_NO_BROWSER	❌	— (set to any value to stop login opening a browser; the URL is always printed)
DIAGRAMS_NO_AUTO_LOGIN	❌	— (set to any value to disable in-tool connect; unauthenticated tools then just say to run login)

Add it to your MCP client

The published package runs straight from npm, so there is no path to fill in and no key in the config. Run npx @diagrams-so/mcp install to print these blocks for your client.

Claude Code (CLI)

claude mcp add diagrams-so -- npx -y @diagrams-so/mcp
npx @diagrams-so/mcp login

Claude Desktop / Cursor (claude_desktop_config.json / mcp.json)

{
  "mcpServers": {
    "diagrams-so": {
      "command": "npx",
      "args": ["-y", "@diagrams-so/mcp"]
      // optional: "env": { "DIAGRAMS_API_BASE": "http://localhost:8000/api/v2" } for a local API
    }
  }
}

Connect either by running npx @diagrams-so/mcp login once, or by asking for a diagram and clicking the link the first tool call gives you. Set DIAGRAMS_API_KEY instead only for CI and headless machines, where no browser can open.

Restart the client, then ask: "Generate an AWS 3-tier web app diagram and show me the warnings."

One-click install (MCPB)

Download diagrams-so.mcpb from the latest release and drag it into Claude Desktop. No terminal, and it no longer asks for an API key: install it, then connect on first use by clicking the link the first tool call gives you.

Building the bundle yourself is a contributor step, see Developing locally.

Verify it works

DIAGRAMS_API_KEY=dgz_live_your_key node test-smoke.mjs

Runs the full flow (connect → list tools → whoami → generate → warnings → fix → export → error handling).

Continuous integration & releases

Workflow	Trigger	What it does
CI (ci.yml)	every push / PR	npm ci + npm run build on Node 18/20/22, then a free smoke (scripts/ci-smoke.mjs) that launches the built server and asserts all 23 tools register. No API calls, no credits.
Live smoke (live-smoke.yml)	nightly + manual	the full end-to-end flow (test-smoke.mjs) against the real API. Spends credits — runs only when the DIAGRAMS_API_KEY secret is set.
Release (release.yml)	tag vX.Y.Z	build → npm prune --omit=dev → pack diagrams-so.mcpb → attach to a GitHub Release. Publishes to npm too if an NPM_TOKEN secret is set.

Cut a release:

# bump "version" in package.json + manifest.json to match, commit, then:
git tag v1.2.0 && git push origin v1.2.0

The tag must match package.json's version (the workflow enforces this). The .mcpb bundle appears on the GitHub Release; manual workflow_dispatch produces it as a downloadable artifact without publishing (handy for testing a bundle).

Repo secrets/variables (optional): DIAGRAMS_API_KEY (live smoke), NPM_TOKEN (npm publish), DIAGRAMS_API_BASE variable (non-prod live-smoke target).

Notes

• stdout is the MCP channel — the server logs only to stderr.
• Errors come back as clean MCP tool errors carrying the API's code, HTTP status, and request_id.
• The server never talks to internal services or the database — only the public /api/v2.
• Long-running tools stay alive past client timeouts. generate / edit / fix / relayout / enhance_prompt / clarify_prompt emit a notifications/progress every 10s while running, so MCP clients that reset their request timeout on progress (resetTimeoutOnProgress) won't abort a slow generation at the SDK's 60s default. If your client doesn't reset on progress, raise its per-call timeout for these tools.

Developing locally

Only needed if you are changing the server itself. Users should install from npm, see Quick start.

git clone https://github.com/RedHold/diagrams-mcp-app-core.git
cd diagrams-mcp-app-core
npm install                  # installs deps and builds dist/ via the prepare hook
node scripts/ci-smoke.mjs    # all 23 tools register; no API calls, no credits

# point a client at your working copy
claude mcp add diagrams-so-dev -- node "$(pwd)/dist/index.js"

# build the MCPB bundle
npm run build && npx @anthropic-ai/mcpb pack