figcraft/docs/mcp.md

FigCraft MCP server

FigCraft ships a Model Context Protocol server so AI agents can design with it: create and edit layers, run any menu command, inspect the result as JSON and look at it as a PNG. It speaks newline-delimited JSON-RPC 2.0 over stdio (MCP protocol 2025-06-18; 2025-03-26 and 2024-11-05 clients are accepted too).

The server lives in crates/mcp (figcraft-mcp) and is started by the CLI:

Command	Backend
figcraft-cli mcp	Headless: an in-process engine session with one untitled document. No window; renders with the CPU renderer.
figcraft-cli mcp --attach <port>	Attached: drives a running FigCraft app through its control channel (figcraft --control <port>). The user sees every change live.

--attach also takes host:port. The control channel only listens on 127.0.0.1.

Configure a client

Build the CLI first (cargo build --release -p figcraft-cli) and use the absolute path to target/release/figcraft-cli.

Claude Code

# headless
claude mcp add figcraft -- /path/to/figcraft-cli mcp
# drive the running app (start it with: figcraft --control 7979)
claude mcp add figcraft-app -- /path/to/figcraft-cli mcp --attach 7979

Or in a project's .mcp.json:

{
  "mcpServers": {
    "figcraft": { "command": "/path/to/figcraft-cli", "args": ["mcp"] }
  }
}

Claude Desktop

claude_desktop_config.json (Settings > Developer > Edit Config):

{
  "mcpServers": {
    "figcraft": { "command": "/path/to/figcraft-cli", "args": ["mcp"] },
    "figcraft-app": { "command": "/path/to/figcraft-cli", "args": ["mcp", "--attach", "7979"] }
  }
}

Conventions agents must know

• Coordinates are page units (1 unit = 1 px at 100% zoom), x right, y down.
• create_node and set_properties take x/y relative to the parent (the page when there is no parent, so they are page coordinates then). inspect_document reports parent-relative x/y plus absoluteBounds in page coordinates.
• Children of an auto-layout frame are positioned by the layout: set layout, gap, padding, mainAlign, crossAlign, sizingH/sizingV instead of x/y. More auto layout props:
  • minWidth / maxWidth / minHeight / maxHeight (px, null removes) bound Hug, Fill and Fixed sizes; a hugging text wider than its max width wraps.
  • absolute: true takes a child out of the flow (it stays where it is and follows its constraints when the frame resizes; Fill becomes Fixed).
  • crossAlign: "baseline" lines up the first text baselines in horizontal layouts (other layers align to the top; nested auto layout frames use their first child's baseline).
  • wrap with crossGap (alias rowGap) for the gap between wrapped rows.
  • Grid (layout: "grid"): gridColumns, gridRows (minimum; rows grow), columnGap / rowGap, track sizes columnTracks / rowTracks as [120, "1fr", "auto"] (px fixed, fr fill share, auto hug) or the layout.setTrack {axis, index, sizing, value?} command; on a child, gridColumn / gridRow (0-based anchor cell, null = placed automatically) and gridColumnSpan / gridRowSpan. inspect reports a grid child's resolved gridCell.
• Every menu action is a command (list_commands), and most commands act on ids when given, else on the selection. New layers become the selection.
• Colours are "#RRGGBB" or "#RRGGBBAA". Inside fills, strokes and effects passed through the MCP tools, color may also be a hex string and gradients can be written {"type": "linearGradient", "stops": ["#7048E8", "#1098AD"]}; the server converts them to the engine's paint JSON.
• Text props (fontFamily, fontStyle, fontSize, lineHeight, letterSpacing, textDecoration, textCase, textFills, fontVariations…) apply to the whole layer, or to chars start..end when given (text.style {id, start, end, …} does the same). Styled ranges come back as styledRuns. Variable fonts: fontVariations (alias variationSettings) sets axis values in user units, e.g. {"wght": 550, "wdth": 85} (null = back to what the style name implies); text.setVariations {variations, replace?} merges instead. text.fonts {family, style?, axes: true} lists a font's axes and named instances (named instances are also valid fontStyle values). OpenType features: features {"liga": false, "tnum": true}.
• Every mutation is one undo step (batch makes several one step). A failing command leaves the document as it was.
• Programmatic calls never open dialogs.
• Verify your work: inspect_document / get_node for numbers, screenshot for pixels.

Tools

Tool	What it does
list_commands {filter?}	Every command: id, label, menu, shortcut, undoable, params doc.
run_command {command, params}	Run any command (e.g. align.left, layout.add, component.create, instance.place (drop an instance at a page point into the frame or auto layout slot under it), component.exposeInstance / instance.exposed (nested instance properties on instances), inspect.code (CSS, SwiftUI or Jetpack Compose for a layer), style.create, variable.bind, proto.interaction.add).
batch {commands: [{command, params}], label?}	Several commands as one undo step (command.batch); all-or-nothing.
create_node {type, x, y, width, height, parent, index, name, text, path, props}	Create a frame, rectangle, ellipse, polygon, star, line, arrow, text, vector, section, component or slice; returns {id, node}.
set_properties {ids, props}	node.set on layers (geometry, fills, strokes, effects, corner radius, auto layout, sizing, constraints, masks (isMask, maskType: alpha|vector|luminance), text…); returns the updated layers.
inspect_document {depth, allPages}	The document as JSON (layer tree, styles, selection, history).
get_node {id, depth}	One layer as JSON.
select {ids}	Replace the selection ([] deselects).
export {ids, format, scale, path?}	png, jpg, svg, webp (pdf when available). Without path, images come back as MCP image content, SVG as text.
screenshot {ids?, scale?, maxSize?, window?}	PNG of the page (with background) or of layers, scaled to fit maxSize (default 1600). window: true captures the app window when attached.
open_file {path} / save_file {path?}	Open .figcraft, .json (FigCraft JSON or REST API file JSON, see below), .svg or an image; save as .figcraft.
undo / redo	Step through history.
pointer {kind, x, y, to?, steps?, tool?, shift, alt, cmd}	Mouse gestures in page coordinates with the current tool: click, double, drag, down, move, up, hover.
key {key, shift, alt, cmd}	A shortcut or key as if typed on the canvas (menu shortcuts, tool keys, Escape, Delete, arrows; text editing keys while editing text).
type_text {text, id?}	Type into the text being edited, or replace the contents of text layer id.
inspect_ui {}	Tool, view and status (and panels/timings when attached).

Editing vectors

Vector edit mode is driven with run_command (or pointer/key for gestures): vector.edit.begin {id} (converts shapes to vectors), vector.edit.state (page-space overlay, the local network and each point's handle mirroring), vector.edit.tool {tool: move|pen|bend|paint|lasso|cut}, vector.edit.select {vertices?, segments?, add?}, vector.edit.selectAll, vector.edit.moveVertices, vector.edit.nudge, vector.edit.position {x?, y?}, vector.edit.setHandle, vector.edit.mirroring {mode: none|angle|angleAndLength}, vector.edit.smooth {smooth?}, vector.edit.bend, vector.edit.addVertex, vector.edit.connect {a, b}, vector.edit.pen {x, y, dx?, dy?} (continues from the pen's open end; clicking a point connects or branches), vector.edit.penEnd, vector.edit.paint {x, y} (paint bucket: fills or unfills the closed area under a page point), vector.edit.cut {segment, t} | {vertex}, vector.edit.lasso {points}, vector.edit.delete, vector.deleteHeal, vector.join / vector.smoothJoin (join the selected points while editing), vector.edit.cornerRadius, vector.edit.end. Point indices refer to network.vertices in vector.edit.state; local coordinates are the layer's own.

Importing REST API file JSON

The JSON returned by the public REST API's file endpoint (GET /v1/files/:key, best with geometry=paths so vectors carry their outlines) and its nodes endpoint opens like any document: open_file {path} (a new, untitled document; the JSON is never saved over) or run_command {command: "file.import", params: {path}} (pages appended to the current document). The result's warnings list what was skipped or approximated (unsupported layer, paint and effect types, prototype interactions, variable bindings, instances of components outside the file, which come in as frames). Pages, the layer tree, geometry, paints, strokes, effects, corners, constraints, auto layout, layout grids, exports, text with styled runs, vectors, components, component sets, instances and component properties are mapped. Image fills keep their imageRef and show a grey placeholder unless the image files sit in an images folder next to the JSON, named by imageRef (images/<imageRef>.png); nothing is fetched from the network.

Tool failures come back as results with isError: true and a message; protocol problems (unknown tool, malformed JSON, wrong parameter types) are JSON-RPC errors. Nothing crashes the server.

Resources

URI	Content
figcraft://document	The active document (like inspect_document at depth 8).
figcraft://commands	The command catalog.
figcraft://node/{id} (template)	One layer with children to depth 2.
figcraft://command/{id} (template)	One command's docs, e.g. figcraft://command/layout.add.

Prompts

Prompt	Arguments
mobile_screen	screen (required), device (default "iPhone 16"), brand_color
design_system	name, primary
landing_page	product (required), width (default 1440), accent
prototype_flow	screens (comma-separated), transition

Each returns a step-by-step plan naming the exact tools and commands to use and how to verify.

Examples

Create a card with auto layout and check it:

{"jsonrpc":"2.0","id":1,"method":"tools/call","params":{"name":"create_node","arguments":{
  "type":"frame","name":"Card","x":100,"y":100,"width":320,
  "props":{"fill":"#FFFFFF","cornerRadius":16,"layout":"vertical","padding":24,"gap":12,"sizingV":"hug",
           "effects":[{"type":"dropShadow","color":"#00000026","offset":[0,4],"radius":16}]}}}}
{"jsonrpc":"2.0","id":2,"method":"tools/call","params":{"name":"create_node","arguments":{
  "type":"text","parent":2,"text":"Ada Lovelace","props":{"fontSize":24,"fontStyle":"Bold"}}}}
{"jsonrpc":"2.0","id":3,"method":"tools/call","params":{"name":"get_node","arguments":{"id":2,"depth":2}}}
{"jsonrpc":"2.0","id":4,"method":"tools/call","params":{"name":"screenshot","arguments":{"ids":[2]}}}

A component with an instance whose text is overridden (ids are the ones earlier calls returned; read the instance's text layer id with get_node):

{"jsonrpc":"2.0","id":5,"method":"tools/call","params":{"name":"run_command","arguments":{"command":"component.create","params":{"ids":[2]}}}}
{"jsonrpc":"2.0","id":6,"method":"tools/call","params":{"name":"run_command","arguments":{"command":"instance.create","params":{"component":2,"x":500,"y":100}}}}
{"jsonrpc":"2.0","id":7,"method":"tools/call","params":{"name":"type_text","arguments":{"id":7,"text":"Grace Hopper"}}}

Align and distribute as one undo step:

{"jsonrpc":"2.0","id":8,"method":"tools/call","params":{"name":"batch","arguments":{"label":"Tidy","commands":[
  {"command":"align.top","params":{"ids":[3,4,5]}},
  {"command":"distribute.horizontal","params":{"ids":[3,4,5]}}]}}}

The end-to-end tests in crates/mcp/tests/agent_tasks.rs are worked examples of ten realistic tasks (auto layout, components and overrides, gradients and shadows, paint styles, Light/Dark variables, align/distribute/group, boolean subtract + flatten, export, undo/redo, drawing with tools).