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Lousa

Creates animated, hand-drawn diagrams that agents can display, update, inspect, and delete through MCP.

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Install Lousa

Pick your client, then add it in one click or paste the config.

STDIONode.js
~/Library/Application Support/Claude/claude_desktop_config.json
claude_desktop_config.json
{
  "mcpServers": {
    "lousa": {
      "command": "npx",
      "args": [
        "-y",
        "lousa"
      ],
      "env": {
        "PORT": "YOUR_VALUE_HERE",
        "HOST": "YOUR_VALUE_HERE",
        "LOUSA_DATA_DIR": "YOUR_VALUE_HERE",
        "LOUSA_BUCKET": "YOUR_VALUE_HERE",
        "LOUSA_TOKEN": "YOUR_VALUE_HERE",
        "LOUSA_URL": "YOUR_VALUE_HERE",
        "LOUSA_DEFAULT_TTL_HOURS": "YOUR_VALUE_HERE"
      }
    }
  }
}

Settings → Developer → Edit Config, merge this into mcpServers, then fully quit and reopen Claude Desktop.

Values are written into the snippet above so you can paste it as is. They never leave your browser.

Install not yet sandbox-tested— we haven't run this command through our automated sandbox yet. Not a red flag; we're working through the catalog.

Overview

The lousa MCP server lets AI agents create and revise animated whiteboard diagrams from declarative JSON scenes. It runs a local web viewer alongside an MCP endpoint, rendering boxes, arrows, notes, and other elements stroke by stroke. Use it when an agent needs to explain architecture, flows, or concepts visually and let a user select parts for follow-up edits. Boards expire after 12 hours by default, or can be retained indefinitely.

Use cases

  • Draw an authentication flow
  • Explain a rate limiter visually
  • Revise a selected diagram section
  • Inspect board elements programmatically
  • Share a temporary architecture whiteboard

Key features

  • Creates animated whiteboard scenes
  • Updates only changed diagram elements
  • Reads user selections from the viewer
  • Supports hand-drawn shapes and connectors
  • Expires boards on a configurable schedule
  • Supports filesystem or S3 board storage

Tools5

What Lousa lets your agent do. Expand a tool for its parameters.

Self-reported~68 tokens of context

Security & health

What it can reach and how reliably it runs — from our own checks, not the maintainer’s claims.

ActiveLast checked 2d ago

Recent health check succeeded.

7/7 checks healthy over the last 40d

Supply-chain signal

No high-severity advisories surfaced by our automated scan.

Critical 0High 0Medium 0Low 0

Scanned 14d ago via OSV.dev · lousa (npm)

Adoption & maintenance

Factual signals from GitHub, npm, and our automated checks — not a rating.

npm downloads136Package downloads in the last 30 days.
Last commit2mo agoMost recent push to the default branch.
Tools exposed5Callable tools this server registers over MCP.

How Lousa works

What lousa MCP server does

The lousa MCP server gives an AI agent a shared whiteboard for visual explanations. Instead of returning only text, the agent builds a scene made from supported elements such as boxes, ellipses, diamonds, cylinders, arrows, lines, text, and notes. The accompanying web viewer renders those elements with a hand-drawn appearance and animates their strokes.

A board is created from a scene and returned with an identifier and viewer URL. Agents can replace the scene later, read board contents, inspect what a viewer user selected, or remove the board. This makes the server suitable for diagrams that evolve through conversation rather than static images.

How it works

The lousa MCP server accepts scenes as JSON arrays. Arrows can connect element IDs, allowing an agent to describe relationships between components. When an update arrives, elements that did not change remain byte-identical, so the viewer can animate only the modified parts instead of redrawing everything.

The viewer supports interaction through element selection. A user can click items in the open board, and get_selection returns the selected IDs together with their complete element data. An agent can then use that context to revise a specific section of a diagram.

Boards normally use a sliding 12-hour expiration period. Setting ttlHours to 0 keeps a board without an expiry. Board URLs function as per-board capability links, while global operations and the MCP endpoint can be protected with a bearer token.

Setup and configuration

Node.js 18.17 or newer is required. For a local stdio setup, configure the MCP host to run npx with arguments -y, lousa, and mcp. Claude Code can add the server with claude mcp add lousa -- npx -y lousa mcp. Running npx lousa directly starts the local server and viewer at http://127.0.0.1:4666.

A shared deployment can bind to another host and use a remote URL. HOST and PORT control the server bind address and port. Filesystem boards are stored under LOUSA_DATA_DIR by default; LOUSA_BUCKET switches storage to S3. Set LOUSA_TOKEN to protect global routes and MCP access, and set LOUSA_URL when the mcp command should proxy to a remote lousa server. LOUSA_DEFAULT_TTL_HOURS changes the default expiry. AWS Lambda and S3 deployments are supported through the included handler and bucket setting.

Tools and capabilities

The available MCP operations are:

  • create_board: creates a board from a scene and returns its ID and URL.
  • update_board: replaces the board scene while preserving unchanged elements for incremental animation.
  • get_board: reads a board.
  • get_selection: returns selected element IDs and full element data from the viewer.
  • delete_board: removes a board.

The scene schema is included in the tool definitions, so agents do not need a separate schema installation.

Limitations and notes

The server is focused on declarative whiteboard scenes, not general image generation or document authoring. It requires a web viewer for visual interaction, and boards are temporary by default unless configured otherwise. A remote deployment needs an HTTPS front end appropriate to its hosting environment, and protected deployments require clients to provide the configured token for global routes and MCP access.

Read the full README View source on GitHub

Reviews

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Frequently Asked Questions about Lousa

lousa is an MCP server that connects AI agents to a live web whiteboard. Its main tools create, update, read, inspect selections from, and delete boards. Agents describe diagrams as JSON scenes containing shapes, connectors, text, and notes, while the viewer renders changes with an animated hand-drawn style.

Run it with Node.js 18.17 or newer using `npx -y lousa mcp` in an MCP host. For Claude Code, use `claude mcp add lousa -- npx -y lousa mcp`. Running `npx lousa` directly starts the local viewer and server.

Yes. lousa uses a standard MCP stdio configuration, so it can be configured in MCP hosts that support that transport, including Cursor. Use `npx` with arguments `-y`, `lousa`, and `mcp`.

Run the server on a Node.js host with a reachable `HOST` and set `LOUSA_URL` on each client that should proxy to it. `LOUSA_TOKEN` can protect the shared server, while `LOUSA_BUCKET` enables S3-backed storage.

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