Lasso MCP server: screen annotation for AI agents

Lasso includes a local Model Context Protocol (MCP) server for Mac. Claude Code, Claude Desktop, Cursor and other clients that support local stdio MCP servers can capture your annotated screen, draw arrows and numbered steps, and sketch on an endless whiteboard after you allow access.

By Nika Sakandelidze · Updated November 4, 2026 · Read as Markdown

When to use Lasso with an agent

Use Lasso when you want to show an agent the exact part of a design, browser or document you mean. Circle it on screen, then ask the agent to inspect it. Use agent drawing for visual instructions, interface feedback or a diagram you can continue editing yourself.

Lasso is a native Mac app with a local stdio MCP connection. It is not a hosted HTTP MCP service or a browser automation API. Its tools capture and annotate; they do not click controls or type into other apps.

Connect Claude Code

Install Lasso in /Applications on a Mac running macOS 14 Sonoma or later. In Terminal, register the app’s MCP bridge with Claude Code:

claude mcp add --scope user lasso -- /Applications/Lasso.app/Contents/MacOS/Lasso --mcp

Connect Claude Desktop, Cursor or another MCP client

Add this server to the client’s MCP configuration. It launches Lasso’s executable with --mcp over stdio; use the actual app path if you installed it somewhere else. Lasso Settings → Agents shows the configuration for the copy you are running.

{
  "mcpServers": {
    "lasso": {
      "command": "/Applications/Lasso.app/Contents/MacOS/Lasso",
      "args": [
        "--mcp"
      ]
    }
  }
}

Allow the connection and screen access

The MCP bridge runs locally on your Mac. Your AI client can send the screenshots and text it receives to its model provider under that client’s privacy settings. Review those settings before showing it sensitive information.

Enable agent access in Lasso Settings → Agents if it is off.
Ask the connected client to use a Lasso tool. Lasso asks you to Allow or Don’t Allow the first tool call.
For capture_screen, allow Lasso in System Settings → Privacy & Security → Screen Recording. Drawing works without that permission.

MCP tool reference

MCP tool reference
Tool	What it does
capture_screen	Returns a display image with your visible annotations and its pixel dimensions. Drawing coordinates start at the top left of that image.
get_screenshot	Returns recent screenshots you took with Lasso, including edits, and a full-size PNG path when available.
draw	Adds arrows, lines, highlights, rectangles, ellipses, pen strokes, text and numbered steps. Marks stick to the window they point at by default; anchor: screen keeps them fixed to the display.
new_board	Opens an endless whiteboard or blackboard page for a diagram.
move_board	Pans or zooms the board, or fits the full sketch in view.
clear_drawing	Removes the agent’s marks while leaving your own marks in place.

Try a visual explanation

Circle a confusing part of an interface, then ask: “Use Lasso to look at what I circled and draw an arrow showing where I should click.” The agent should call capture_screen before choosing coordinates for draw. You can add to its drawing, pin the marks to click through them, or press Escape to clear the page.

For a diagram, ask: “Use Lasso to sketch this flow on a whiteboard, then fit it in view.” The agent can use new_board, draw and move_board. It can inspect each tool’s current argument schema through MCP tools/list.

If the client cannot connect

Check that /Applications/Lasso.app/Contents/MacOS/Lasso exists, that the client is configured for a local stdio server, and that --mcp is included in its arguments. Reconnect or restart the client after changing its configuration. If a screen capture is refused, check Lasso’s Screen Recording permission. Agent access can be changed in Settings → Agents.