Sketch Agent Bridge

Sketch Agent Bridge connects older versions of Sketch to AI agents such as Claude Code, and it is built and tested against Sketch 88.1. It adds a plugin and a local MCP server that let an agent read designs from the open Sketch document and edit it.

What it does

An agent connected to the MCP server can do the things listed below in the open Sketch document.

Read the design

• see the current selection as a PNG, an SVG, and a JSON spec of its layers

• list pages and artboards, and read any layer by id

• find layers by type, name, text, symbol, shared style, or swatch, and list symbols with how many instances use each one

• read the document's design tokens, which are its swatches, text styles, layer styles, and symbols

• read the lines a text layer wraps into, and whether the text overflows its frame

• find text layers that another layer crosses, such as a shape drawn over a heading

• see which layers no longer match their shared style

Create layers

• build a whole tree of artboards, groups, shapes, paths, text, SVG drawings, and images in one call

• download the Unsplash photos most relevant to a query, filtered by orientation or color, with a credit for each photographer, for use as image layers and fills

Fonts

• list the installed font families and the weights and styles of each one

• download a family from Google Fonts into ~/Library/Fonts and add it to a "Google Fonts" collection in Font Book

Edit layers

• edit layers, move them into other artboards, groups, or pages, lock them, group and ungroup them, and apply shared styles

• change several layers in one call, and replace the drawing in an SVG layer

• duplicate layers, change their stacking order, rotate and flip them, and set Smart Layout on groups and symbols

• fill layers with colors, gradients, or images, add inner shadows, blurs, blend modes, dashed borders, and arrowheads, and set Sketch's Color Adjust on image layers

• edit the points of a path, and set line spacing and variable font axes on text

• style part of a text layer, such as one bold or colored word

• use a shape or image as a clipping mask for the layers above it in its group

• combine shapes with union, subtract, intersect, and difference

• pin layers to the edges of their group, artboard, or symbol and fix their width or height, which sets how they change when a symbol instance is resized

• set the column, row, and square grids on artboards and symbol masters

Symbols, styles, and libraries

• turn layers into symbols, place instances, set their overrides, swap them between symbols, and detach them

• set which overrides a symbol lets its instances change

• turn artboards into symbols and back

• add or change swatches and shared styles

• use symbols, shared styles, and swatches from enabled libraries by name, sync or unlink them, and add libraries or turn them on and off

Prototypes and exports

• link layers and hotspots to artboards for prototypes

• export layers as PNG, SVG, or Sketch's JSON file format, with a background color or without cropping to the visible content

• add export presets and slices

Pages and the document

• add, rename, reorder, and delete pages

• switch Sketch to a layer's page, select layers, and scroll the canvas to a layer

• read and change the document's color space

• save the document when the user asks

Without MCP

For agents without MCP support, the plugin menu command Plugins > Agent Bridge > Send Selection to Agent exports the selection to a folder and copies the folder path to the clipboard, so the path can be pasted into any agent.

Related MCP server: AI-Canvas MCP Server

How it works

The MCP server runs sketchtool run, the command-line tool that comes with Sketch, to call a command in the plugin. The plugin runs the command inside Sketch and writes its reply and exports to ~/.sketch-agent-bridge/.

Setup

Build the server in Docker, connect it to an agent, and optionally link the plugin into Sketch for the menu command. The steps are in docs/install.md, and the request and reply format is in docs/protocol.md.

Safety

• build_layers and create_artboard put new layers on a page named "Agent Drafts" unless the agent names another parent or page.

• Before the first edit in a session, the server copies the .sketch file to ~/.sketch-agent-bridge/backups/ and keeps the newest 10 copies of each file.

• Each edit is one step in Sketch's undo history. If Sketch stops recording undo history for the document, every edit reply starts with a warning until Sketch restarts.

• The agent can only delete layers, detach symbol instances, delete pages, or turn symbol masters into artboards when it created them, unless it passes force: true.

• update_library changes Sketch's library list for every document, outside the backup and Cmd+Z, and it can add or turn off a library but not remove one.

• The bridge makes network calls only through two tools. fetch_images calls api.unsplash.com and downloads photos from images.unsplash.com, and install_google_font calls fonts.googleapis.com and downloads fonts from fonts.gstatic.com. The server reads the Unsplash key from the login keychain, or from UNSPLASH_ACCESS_KEY when the keychain has no key, and sends it only to api.unsplash.com.

• Apart from the .sketch file that save_document saves, every file the bridge writes stays under ~/.sketch-agent-bridge/ on the Mac, except for the font files that install_google_font adds to ~/Library/Fonts and the "Google Fonts" collection that macOS saves to ~/Library/FontCollections/. install_google_font never replaces a font file that is already there.

• The plugin reads image and SVG files only from ~/.sketch-agent-bridge/ and the folders listed in SKETCH_AGENT_BRIDGE_ASSET_DIRS. The folders under ~/.sketch-agent-bridge/ can be read only by the user who owns them.

License

GPL 3.0. See LICENSE.