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:
  • sizingH / sizingV: fixed, hug (auto layout frames and text) or fill (children in an auto layout flow). A child can't fill an axis its parent hugs: setting fill turns the parent fixed on that axis, and a parent set to hug turns the children that filled it fixed. A layer moved out of auto layout (or whose frame loses it) keeps its size as fixed. Fill children share the space like CSS flexbox, within their min/max.
  • 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.
• Colour profile: colour values are in the file's profile, sRGB (default) or Display P3 (inspect_document reports colorProfile). file.colorProfile {profile: srgb|displayP3, convert?} changes it: convert (default true) converts every colour value so colours keep their appearance; false keeps the values and reinterprets them. Images are treated as sRGB and managed into the file's space. PNG exports are tagged (sRGB chunk, or a Display P3 ICC profile plus cICP), Display P3 JPG and WebP embed the ICC profile, and SVG and PDF export Display P3 files converted to sRGB (out-of-gamut colours clip).
• Image adjustments: image paints carry filters (exposure, contrast, saturation, temperature, tint, highlights, shadows; each -1..1). image.adjust {ids?, target?: fill|stroke, index?, preset?, filters?} applies a built-in preset (vivid, muted, warm, cool, blackAndWhite, fade, reset) or one saved in the file, with any filters values on top. image.savePreset {name, filters?} saves the current (or given) adjustments in the file, image.deletePreset {name} removes one and image.presets lists both kinds.
• 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), component.makeSlot / instance.slotInsert / instance.resetSlot (slots, below), inspect.code (CSS, HTML + CSS for a whole frame, SwiftUI or Jetpack Compose for a layer), inspect.properties (layout, auto layout, typography, fills, strokes and effects with their style and variable names), inspect.assets (layers under the selection with export settings), style.create, variable.bind, variable.update (rename, describe, scope), variable.set with {alias}, variable.renameMode / variable.removeMode, variable.deleteCollection, 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), handoff status (devStatus: none|readyForDev|completed), 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 | size, path?}	png, jpg, svg, webp, pdf; size is 2x, 512w or 512h. Without path, images come back as MCP image content, SVG as text. Layers' own export settings: run_command with export.add / export.update {index, size?, suffix?, format?} / export.remove and file.exportLayers {ids?, dir?} (every layer once per setting, named <layer><suffix>.<format>).
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, variables?} / save_file {path?}	Open .figcraft, .json (FigCraft JSON or REST API file JSON with its variables, 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|eraser}, 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.erase {points, radius?} (the eraser), 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.

Prototypes

Interactions are proto.interaction.add / set / remove / clear (a navigate action can keep the scroll position with preserveScroll: true), flows proto.flow.add / rename / remove, and the device and background proto.settings {device?, background?} (None, iPhone 16, iPhone 16 Pro Max, Android Compact, iPad mini, MacBook Air, Desktop). On a device the presented frame is sized to the device's screen: what doesn't fit is clipped, or scrolls when the frame's overflow allows it, while fixed layers stay on screen (pinned to the edges their constraints name). proto.present {start?} plays the prototype full-window and proto.preview {start?} in a resizable pane over the canvas that follows edits live; proto.closePreview closes it. The player's state is in inspect_ui (presenter, preview) when attached, and ui.set {presentScroll: [x, y]} scrolls its screen (see control-protocol.md).

Local libraries

A .figcraft file can be published as a library and used from other files (local files only: no accounts, nothing on the network; the browser build has no file system, so there the commands that read library files return an error).

• Publish (in the library file): library.publish {description?, include?, exclude?} publishes the file's components, component sets, styles and variable collections as a new version (by default everything except names starting with . or _, or what the last publish offered; include/exclude take component ids and style or collection ids or names). A collection comes with its variables (values per mode, aliases, scopes), except those hidden from publishing (variable.update {variable, hiddenFromPublishing: true}). Components, styles and variables that published assets use (a component's bound variables, a variable's alias targets) come along, unoffered. Each asset keeps the version it last changed in; publishing with no changes is refused. Save the file (file.save) so other files see the new version.
• Enable: library.add {path} / library.remove {id} (id, name or path) / library.list {assets?} (versions, pending updates, errors; with assets: true each library's components, styles, variable collections (with their modes) and variables, and what this file can publish). Libraries are read read-only with size limits, and read again when the file changes.
• Use: library.place {library, component, x?, y?} (a component, set or variant by id or name; page point, default the view's centre) copies the component, with the components and styles it uses, into the file as a read-only main component and places an instance; library.import {library, component} only copies it (then instance.create, instance.swap…). library.applyStyle {library, style, ids?, target?} copies a style in (linked, read-only) and applies it. Instances of library components behave like any instance: overrides, properties, variants, swap, reset, detach. Library components keep their variable bindings and explicit modes (bound to copies of the library's variables).
• Library variables: library.bindVariable {library, variable, field, ids?} copies a published variable in (linked, read-only, with the variables it aliases and its collection) and binds it like variable.bind; library.aliasVariable {library, alias, variable, mode?} makes a local variable's value an alias of a library variable; library.setVariableMode {library, collection, mode, ids?} sets a library collection's mode on frames (the page when no ids are given); library.importVariable {library, variable} only copies it (then variable.bind, variable.set {value: {alias}}). The copies render without the library file. Editing the copies (library components, styles, variables or collections) is refused; edit the library file and publish.
• Update: library.updates lists the components, styles, variable collections and variables with a newer published version; library.acceptUpdates {ids? (library ids)} pulls them in, keeping instance overrides; bound layers, aliases and explicit modes follow the updated values.

Slots

A slot is a frame inside a main component whose instances take any content of their own (add, remove and reorder layers there, unlike the rest of an instance). It is a component property of type slot (component.properties lists it: on a main with its layers, on an instance with value: {layer, edited, layers}).

• Define (on the main): component.makeSlot {id (a frame inside a main component), name?, preferred? [component or set ids]} (the property is named after the frame by default); component.editProperty {name, preferred}; component.removeSlot {id} (instances lose their own content in it). component.addProperty {type: "slot", layer} and component.bindProperty {field: "slot"} work too (one frame per component for a slot).
• Fill (on an instance): instance.slotInsert {id (the slot layer, or the instance with slot (property name)), component, index?, replace?} places an instance of a component in it; any structure command (shape.*, node.reparent, edit.paste with the slot selected, edit.delete, node.reorder, instance.place or a drag onto it) works inside it. The main's default content shows (and follows the main) until the slot is first edited; then the slot's layers are the instance's own (override group slot): kept across main updates, variant switches, copy/paste and detach, and instances placed there stand alone (their own overrides, properties and detach).
• Reset: instance.resetSlot {id} (or component.resetOverride {id, group: "slot"}, or component.resetInstance) brings back the main's default content.

get_node shows "slot": "<property>" on slot layers.

Shape builder

The selected shapes' outlines split the canvas into regions (areas covered by the same shapes). shapeBuilder.regions {ids?} lists them: an SVG path in page coordinates, the sources covering each one (top-most first), bounds and a point inside. shapeBuilder.merge {ids?, regions?, points?} makes one vector from the regions (by index, or the regions under page points), styled like the top-most shape over the first one; shapeBuilder.remove {ids?, regions?, points?} deletes them. Either way every shape covering a picked region loses that area (it becomes a vector, or goes when nothing is left), and each call is one undo step. The tool is tool.shapeBuilder (Shift+M): click or drag across regions with pointer to merge, add alt to remove; shapeBuilder.mode {mode: merge|remove} swaps what a plain click does.

{"jsonrpc":"2.0","id":1,"method":"tools/call","params":{"name":"run_command","arguments":{"command":"shapeBuilder.regions","params":{"ids":[2,3]}}}}
{"jsonrpc":"2.0","id":2,"method":"tools/call","params":{"name":"run_command","arguments":{"command":"shapeBuilder.merge","params":{"ids":[2,3],"points":[[120,80],[160,80]]}}}}

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, with their flows, prototype settings and variables). The result's warnings list what was skipped or approximated (unsupported layer, paint and effect types, video and gamepad triggers, conditional and variable-mode actions, bindings to library variables, 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, and so is prototyping: interactions (on click, hover, press, drag, after delay, mouse enter/leave/down/up and key triggers; navigate, overlays, back, scroll to, change to, open link and set variable actions; dissolve, smart animate, move, push and slide transitions with their easing, custom bezier and spring curves included), flow starting points, scroll overflow and fixed/sticky layers, and the prototype device. 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.

Variables come from the local variables response (GET /v1/files/:key/variables/local): collections with their modes (the default mode first), values per mode, aliases and scopes. Pass it as variables (a path, or the JSON object or text) to open_file, file.open or file.import, put it next to the file as <name>.variables.json or variables.json, or embed its meta in the file JSON. Layers' boundVariables (sizes, gaps and padding, corner radii, opacity, stroke weight, visibility, text, font properties, single solid fills and strokes) and explicitVariableModes then link to them, so switching a mode with variable.setMode restyles the layers.

Version history

Named snapshots of the document, kept in the .figcraft file (they persist once the file is saved; a new, renamed or deleted version marks the file as changed). Driven with run_command: file.saveVersion {name?, description?} (returns {id, index, name, description, time}; untitled versions are named "Version N"), version.list (oldest first; time is Unix seconds), version.restore {id | index} (replaces the document with the version as one undo step; the file name stays), version.rename {id | index, name, description?}, version.delete {id | index} and version.duplicate {id | index} (opens the version as a new document tab). version.preview {id | index} shows a version in place of the document, read-only: edits, undo and gestures are refused until version.restore keeps it or version.exitPreview goes back. Saving, closing or saving a version ends the preview first, and version.list marks the shown version previewing. Indexes are validated (a negative or out-of-range index is an error). A file keeps at most 100 versions. version.autosave saves an automatic checkpoint (auto: true, named "Autosave") when the document has unsaved changes since its last version; the app runs it every 30 minutes for each open document, and a file keeps the newest 20 autosaves (user versions are never dropped for them). file.versionHistory returns the same list and opens the panel in the app.

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).