framesmith

An open-source MCP server that gives your AI coding agent a visual canvas. Sketch the UI, review it in a browser, agree on the design — before any framework code gets written.

Contents: Viewer · Installation · Tools · Usage Example · Workflow · Development

Above: the framesmith viewer. Workspaces and projects in the sidebar, canvases as live thumbnails on the right. AI agents create canvases via MCP tools; you browse them like Figma files.

MCP Client → stdio → framesmith server
                        ↓
              Scene Graph (in-memory JSON tree)
                        ↓
              HTML/CSS Renderer (inline styles)
                        ↓
              Puppeteer (headless Chromium → PNG)

Viewer

Run npx -p framesmith framesmith-viewer to start the standalone browser viewer (default port 3001). Open any canvas to review it at multiple breakpoints, compare them side-by-side, inspect the underlying JSON, or archive / delete.

Above: a single canvas in the detail view. The toolbar across the top exposes the breakpoint preview modes, Compare for side-by-side rendering, Fit for max-width, JSON for the raw scene graph, and lifecycle actions.

The viewer is purely read-only — every canvas is authored through MCP tool calls from your AI assistant. Files persist to ~/.framesmith/canvases/ so the viewer keeps showing them across sessions.

Installation

No clone or build needed — register framesmith with your MCP client via npx (requires Node 20+).

Claude Code

claude mcp add framesmith -- npx -y framesmith

Codex

Add to ~/.codex/config.toml:

[mcp_servers.framesmith]
command = "npx"
args = ["-y", "framesmith"]

Cursor

Add to ~/.cursor/mcp.json (or per-project .cursor/mcp.json):

{
  "mcpServers": {
    "framesmith": {
      "command": "npx",
      "args": ["-y", "framesmith"]
    }
  }
}

Windsurf

Add to ~/.codeium/windsurf/mcp_config.json:

{
  "mcpServers": {
    "framesmith": {
      "command": "npx",
      "args": ["-y", "framesmith"]
    }
  }
}

VS Code + MCP extension

Add to .vscode/mcp.json (project-scoped) or your global MCP settings:

{
  "servers": {
    "framesmith": {
      "command": "npx",
      "args": ["-y", "framesmith"]
    }
  }
}

Any other MCP-compatible client

framesmith speaks standard stdio MCP. Point your client at npx -y framesmith using whatever config shape your client expects.

Optional: set FRAMESMITH_VIEWER_URL=http://localhost:3001 in the MCP server env to pin it to a long-lived standalone viewer process — see Running the viewer.

Build from source (for development)

git clone https://github.com/vicmaster/framesmith.git
cd framesmith
npm install
npm run build
# then point your client at: node /path/to/framesmith/dist/index.js

Tools

init

One-call onboarding — the recommended first call each session, and safe to run repeatedly (idempotent). Binds the current repo if it isn't already (canvases become checked-in JSON under .framesmith/), ensures the convention projects exist, and returns the live state you need to start working.

Param	Type	Description
dir	string?	Directory to bind / detect. Defaults to the nearest git repo root above the server working directory.
workspaceName	string?	Name for the workspace when binding fresh. Defaults to the repo folder name.
projects	string[]?	Projects to ensure exist (default: ["Foundations", "UI"]). Existing projects are never removed, so it's safe for adding feature/area projects like Onboarding.

Returns the bound workspace + project IDs (binding re-keys IDs to repo-* — use the ones init returns), the on-disk layout, the workspace-layer token count, a workflow cheatsheet, the current gotchas, the framesmith://guidelines URI, and the viewer URL. It does not seed design tokens — set those at the workspace layer with workspace_set_design_system. The default Foundations project is just a canvas that visualizes the workspace tokens (which is where the design system actually lives).

canvas_create

Create a new canvas. If projectId is omitted, it lands in the built-in Untitled project of the Personal workspace.

Param	Type	Description
name	string?	Canvas name
projectId	string?	Target project. Defaults to the built-in Untitled project. See project_list.

The response also carries a diversification signal for the target project: the recently-built structures (newest first) and a hint to differ on at least one taxonomy axis, so successive canvases don't converge on the same layout. It's advisory — never blocking.

canvas_list

List canvases. Excludes archived canvases by default.

Param	Type	Description
projectId	string?	Scope to one project
includeArchived	bool?	Include archived canvases (default false)

Returns [{ id, name, createdAt, lastModified, projectId, archived }].

canvas_move / canvas_archive / canvas_unarchive / canvas_delete

Canvas lifecycle. canvas_move reassigns a canvas to a different project. canvas_archive sets a soft-delete flag (canvas stays on disk, hidden from default canvas_list); canvas_unarchive clears it. canvas_delete removes the canvas and its file permanently — irreversible.

viewer_url

Get the URL of the live viewer plus per-canvas URLs. Share these with the user so they can open the design in their browser. No params.

{
  "url": "http://localhost:3001",
  "gallery": "http://localhost:3001",
  "canvases": [
    { "name": "Login", "viewer": "http://localhost:3001/canvas/abc123" }
  ]
}

canvas_create already returns the per-canvas viewer URL in its response; reach for viewer_url when you want the gallery URL or to enumerate every existing canvas's URL in one call.

workspace_create / workspace_list / workspace_rename / workspace_delete

Top-level container CRUD. The built-in Personal workspace cannot be deleted, and workspace_delete refuses if the workspace still contains projects (move or delete them first).

project_create / project_list / project_rename / project_delete

Mid-level container CRUD inside a workspace. The built-in Untitled project cannot be deleted. project_delete refuses if the project still contains any canvases (archived ones still count — move or delete them first).

canvas_bind

Bind a workspace to the current project directory so its canvases live in the repo as open JSON — a .framesmith/ directory checked in alongside the code, instead of the global ~/.framesmith store. Run it once per repo.

Param	Type	Description
workspaceId	string?	Workspace whose projects + canvases migrate into the repo. Defaults to the built-in Personal workspace.
dir	string?	Directory to bind. Defaults to the nearest git repo root above the server's working directory.

It creates .framesmith/workspace.json (the binding plus the design system, so a fresh clone resolves tokens identically) and one subdirectory per project holding one slug-named file per canvas:

.framesmith/
  workspace.json     # workspace + projects[] + design system
  design-system/
    design-tokens.json
  ui/
    bloom-landing.json
    login-form.json

It migrates the workspace's projects + canvases in and makes the repo the source of truth for the rest of the session. A canvas is either repo-bound or global, never both. Afterwards the server auto-detects .framesmith/ on startup (walking up from its working directory). Commit .framesmith/ so designs travel with the code and diff cleanly in review.

The bind also records the repo in ~/.framesmith/registry.json, so the standalone viewer shows bound repos alongside your global workspaces in one gallery (it rebuilds that read-only mirror on launch and whenever the registry changes).

batch_design

Execute operations on the scene graph. Operations are line-separated strings:

# Insert a frame into the document root
header=I("document", { type: "frame", layout: "horizontal", fill: "#1a1a2e", padding: 24, gap: 16, width: 1440, height: 80 })

# Insert text into the header
I(header, { type: "text", content: "My App", fontSize: 24, fontWeight: 700, color: "#ffffff" })

# Update a node
U("nodeId", { fill: "#e94560" })

# Delete a node
D("nodeId")

# Copy a node to a new parent
copy=C("sourceId", "parentId", { fill: "#0f3460" })

# Move a node
M("nodeId", "newParentId", 0)

# Replace a node entirely
R("nodeId", { type: "text", content: "Replaced" })

Returns { ok, nodeIds, results }. nodeIds maps each bound variable to the node ID it created — e.g. { "header": "n_a1b2" } — so you can target those nodes in later calls (bindings only live within a single call). results lists each op's outcome in order.

Node types: frame, text, rectangle, ellipse, image, icon, path, component, instance

Properties: fill, gradient, stroke, strokeWidth, cornerRadius, width, height, layout ("horizontal" | "vertical"), gap, padding, alignItems, justifyContent, fontSize, fontFamily, fontWeight, color, content, src, objectFit, opacity, shadow, shadows, blur, backdropBlur, backdropFilter, overflow, wrap, position, x, y, icon, iconSize, iconColor, d, viewBox, strokeLinecap, strokeLinejoin, animation, transition, componentId, overrides

screenshot

Render canvas to PNG (returned as base64 image).

Param	Type	Description
canvasId	string	Canvas ID
nodeId	string?	Specific node to capture
width	number?	Viewport width (default 1440)
height	number?	Viewport height (default 900)
scale	number?	Device scale (default 2)

read_nodes

Read node data from the scene graph.

Param	Type	Description
canvasId	string	Canvas ID
nodeIds	string[]?	Node IDs to read (default: root)
maxDepth	number?	Max traversal depth (default 5)

snapshot_layout

Get computed bounding boxes via browser rendering.

Param	Type	Description
canvasId	string	Canvas ID
nodeId	string?	Root node to start from
maxDepth	number?	Max depth (default 10)

get_variables / set_variables

Read and write design tokens (colors, spacing, radius, typography). Use $tokenName in node properties to reference variables.

{
  "colors": { "primary": "#e94560", "bg": "#1a1a2e" },
  "spacing": { "sm": 8, "md": 16, "lg": 24 },
  "radius": { "sm": 4, "md": 8 }
}

Then use in nodes: { fill: "$primary", padding: "$md", cornerRadius: "$sm" }

workspace_set_design_system / workspace_get_design_system / workspace_apply_preset

Set tokens at the workspace level — every project + canvas under the workspace inherits them. Resolution order at render is canvas.variables (override) → project.designSystem → workspace.designSystem → built-in defaults, with the rightmost layer winning. Per-category merge: setting only colors doesn't reset spacing.

workspace_set_design_system({
  workspaceId: "...",
  variables: {
    colors: { primary: "#f59e0b", bg: "#0a0a0a" },
    spacing: { sm: 8, md: 16, lg: 24 }
  }
})

workspace_apply_preset({ workspaceId, preset }) is a shortcut that copies a named preset ("dark", "light", "material", "minimal") into the workspace.

project_set_design_system / project_get_design_system / project_apply_preset

Same shape, but at the project layer between workspace and canvas. Use for sub-brand overrides (e.g., a Marketing project that overrides one color while inheriting everything else from the workspace).

get_fonts / set_fonts

Register custom font faces on a canvas. The renderer emits @font-face blocks in <head> plus a <link rel="preconnect"> for unique remote origins, and declares font-display: swap so paint isn't blocked while a font loads.

{
  "fonts": [
    { "family": "Inter", "url": "https://fonts.gstatic.com/s/inter/v18/...regular.woff2", "weight": 400 },
    { "family": "Inter", "url": "https://fonts.gstatic.com/s/inter/v18/...bold.woff2",    "weight": 700 }
  ]
}

URLs must point at the binary (.woff2 / .woff / .ttf / .otf or a data: URI) — Google Fonts CSS stylesheet URLs (fonts.googleapis.com/css2) are not supported, use the gstatic.com binary URL directly. After registering, reference the family on any text node: fontFamily: "Inter, system-ui, sans-serif".

export

Export a canvas or specific nodes to files on disk.

Param	Type	Description
canvasId	string	Canvas ID
format	string	"png", "jpeg", "webp", or "pdf"
outputPath	string	Directory to save files
nodeIds	string[]?	Specific nodes to export (default: full canvas)
width	number?	Viewport width (default 1440)
height	number?	Viewport height (default 900)
scale	number?	Device scale (default 2)

list_presets

List available style guide presets. No params. Returns preset names and descriptions.

apply_preset

Apply a style guide preset to a canvas. Merges preset design tokens into the canvas variables, and copies in any reusable components (button, card, badge) the preset defines so they can be instanced. The preset is also recorded in the canvas provenance + per-project build log.

Param	Type	Description
canvasId	string	Canvas ID
preset	string	Preset name: "dark", "light", "material", "minimal"

list_structures

List available layout structures — named page scaffolds you stamp onto a canvas and then populate. Returns each structure's name, description, and taxonomy axes. Distinct from presets: structures define layout skeleton, presets define color/token theme — they compose.

Param	Type	Description
projectId	string?	If given, also return a diversification signal for the project (recently-built structures + a hint to differ on ≥ 1 axis), so you pick a shape that contrasts with recent work. Omit it to get just the structure list.

Built-in: marquee-hero, bento-grid, stat-led, editorial-longform, split-workbench, catalogue. Each is tagged on four independent axes — heroTreatment, density, rhythm, alignment — so you can deliberately vary page shape instead of defaulting to the same layout.

apply_structure

Stamp a layout structure onto a canvas: inserts the scaffold of labeled placeholder nodes under the canvas root, records provenance, and returns the placeholder node IDs to populate. Seeds neutral default colors so the scaffold renders even before a preset is applied. Populate the placeholders with batch_design U ops, then screenshot to verify.

The chosen structure + axes are stamped onto the canvas (metadata.provenance) and appended to a per-project build log, which feeds the diversification signal on canvas_create / list_structures. Provenance is shown on the canvas's viewer detail page.

Param	Type	Description
canvasId	string	Canvas ID
structure	string	Structure name (use list_structures, e.g. "marquee-hero", "bento-grid")
replace	boolean?	If the root already has children, clear them before stamping. Default false (refuses on a non-empty canvas)

import_design_md

Import a DESIGN.md file as a design system preset. Parses the Google Stitch format and extracts colors, typography, spacing, and border radius. It also extracts reusable component skeletons (button, card, badge) from the "Component Styling" section — apply_preset then makes them available as instanceable components on the canvas. After importing, use apply_preset to apply it to any canvas.

Param	Type	Description
content	string?	Raw DESIGN.md content (provide this OR filePath)
filePath	string?	Absolute path to a DESIGN.md file
name	string?	Override the preset name

Compatible with the 55+ design systems in awesome-design-md (Stripe, Notion, Figma, Vercel, Linear, etc.).

Accepted token formats. Each category is read from a loosely-matched heading section (Colors / Color Palette, Spacing, Border Radius / Radius, Typography). Within a section, tokens may be written as a list item (- name: value), a 2-column table row (| name | value |), or a name: value / **name** (\value`) line — where value is a color (#hex, rgba(...)) for colors, Npxfor spacing/radius, andNpx(optionally/ weight, e.g. 16px / 600) for typography. Named spacing tokens (md: 12px) are honored verbatim; a scale is synthesized **only** when no named tokens are given and a Base unit: Npxis stated — otherwise nothing is fabricated. Radius accepts the scale namessm/md/lg/xl/full/pill`.

screenshot_responsive

Render a canvas at multiple viewport sizes. Defaults to mobile (390x844), tablet (768x1024), and desktop (1440x900).

The renderer emits clamp() for paddings ≥ 32px and font sizes ≥ 24px, so headlines and large spacing shrink proportionally at narrower viewports (assuming a 1440px design width). Smaller values stay static.

Param	Type	Description
canvasId	string	Canvas ID
breakpoints	array?	[{label, width, height}] — custom breakpoints
scale	number?	Device scale (default 2)

canvas_diff

Compare two canvases visually. Returns a diff image with changed regions highlighted in red.

Param	Type	Description
canvasId1	string	First canvas ID
canvasId2	string	Second canvas ID
width	number?	Viewport width (default 1440)
height	number?	Viewport height (default 900)
scale	number?	Device scale (default 1)

canvas_evaluate

Auto-score a design against quality heuristics. Returns an overall score (0–100), per-category scores, and per-node actionable issues. Designed for generator-evaluator loops: build with batch_design, score with canvas_evaluate, fix the issues targeting the returned nodeIds, repeat.

Param	Type	Description
canvasId	string	Canvas ID to evaluate
mode	"fast" | "detailed" | "llm"	"fast" = JSON-tree analysis only (<100ms). "detailed" adds Puppeteer-based pixel-level overlap checks. "llm" runs fast-mode heuristics plus a vision-model critique (provider picked from FRAMESMITH_LLM_PROVIDER or whichever of ANTHROPIC_API_KEY / OPENAI_API_KEY is set — costs one paid API call per invocation). Default "fast".
categories	string[]?	Subset of spacing, color, typography, structure, consistency, cliche. Defaults to all.
genre	string?	Style that relaxes specific cliche gates (e.g. "material" allows purple). Defaults to the canvas's provenance preset if stamped.

Categories and what they check

Category	Weight	Checks
spacing	20	Off-scale padding/gap values, too many unique spacing values
color	25	WCAG AA contrast ratios for text against nearest background
typography	20	Type-scale ratios (1.15–1.75), font-family count, weight variation
structure	15	Tree depth, naming coverage, design-token usage %, component reuse
consistency	20	Frames missing layout, inconsistent sibling padding, sibling overlap (detailed mode)
cliche	15	Machine-made tells: default purple/indigo accent, gradient/glow overuse, fake browser/OS chrome (traffic-light dots), the hanging eyebrow-beside-heading header, fabricated metrics/testimonials/logos. Each issue carries a tell discriminator; all advisory (warning/info). Relaxable per genre.

Return shape

{
  "overallScore": 87,
  "categories": [{ "name": "spacing", "score": 90, "issueCount": 1, "weight": 20 }],
  "issues": [
    {
      "category": "color",
      "severity": "error",
      "nodeId": "abc123",
      "message": "Text \"Sign In\" has contrast ratio 2.8:1 against #1a1a2e. WCAG AA requires 4.5:1.",
      "suggestion": "Increase contrast by darkening/lightening the text or background."
    }
  ],
  "summary": "Overall quality: Good (87/100). Strongest: spacing (90/100). Weakest: color (75/100)...",
  "stats": { "totalNodes": 14, "textNodes": 5, "frameNodes": 8, "maxDepth": 4, "tokenUsagePercent": 61, "componentReusePercent": 0 },
  "mode": "fast"
}

With mode: "llm" (Phase 13), the vision model scores a fixed rubric — five axes, each 1–5 with a rationale — instead of one opaque number. The verdict is stamped on the canvas (metadata.critique) and the per-project build log so quality is auditable over time. Add floor (1–5, default 3, or FRAMESMITH_CRITIQUE_FLOOR) to set the per-axis threshold that trips needsRevision.

{
  "llmCritique": {
    "provider": "anthropic",
    "model": "claude-sonnet-4-6",
    "rubric": {
      "hierarchy":   { "score": 4, "rationale": "clear primary metric, secondary stats recede" },
      "execution":   { "score": 4, "rationale": "tidy alignment and consistent spacing" },
      "specificity": { "score": 3, "rationale": "reads a touch generic for a dashboard" },
      "restraint":   { "score": 5, "rationale": "flat surfaces, no gratuitous effects" },
      "variety":     { "score": 2, "rationale": "the default centered three-card row" }
    },
    "score": 72,
    "summary": "Clean, restrained dashboard; layout is conventional.",
    "suggestions": ["break the symmetric three-card row with an asymmetric feature tile"],
    "needsRevision": true,
    "failingAxes": [{ "axis": "variety", "score": 2, "rationale": "the default centered three-card row" }]
  }
}

Axes: hierarchy (focal order), execution (craft — alignment/spacing/contrast), specificity (designed-for-purpose vs generic), restraint (no overdone effects — the LLM sibling of the cliche category), variety (avoids same-shape sameness). score is derived: round(mean(axisScores) / 5 * 100). To close the loop automatically, see canvas_revise.

Provider selection: FRAMESMITH_LLM_PROVIDER env var (anthropic | openai), else falls back to whichever of ANTHROPIC_API_KEY / OPENAI_API_KEY is set. Default models: claude-sonnet-4-6 / gpt-4.1 (override via FRAMESMITH_LLM_ANTHROPIC_MODEL / FRAMESMITH_LLM_OPENAI_MODEL). Adding a third provider is one entry in the judges table in src/llm-judge.ts.

Example generator-evaluator loop

batch_design({ canvasId, operations: "..." })
const r = canvas_evaluate({ canvasId, mode: "fast" })
// r.issues[].nodeId points to exactly what to fix
batch_design({ canvasId, operations: `U("${r.issues[0].nodeId}", { color: "#ffffff" })` })
canvas_evaluate({ canvasId })  // re-score

Issues that have a mechanical fix come back with an extra fix: { op, rationale } field — see canvas_autofix below.

canvas_autofix

Runs canvas_evaluate in fast mode and returns just the subset of issues with a mechanically derived fix — no judgement calls. Each fix carries a ready-to-paste batch_design Update op string. Closes the generator-evaluator loop without a second AI hop.

Param	Type	Description
canvasId	string	Canvas to autofix
categories	string[]?	Restrict to fixes from these categories (default: all)
genre	string?	Style that relaxes specific cliche gates (e.g. "material" allows purple). Defaults to the canvas's provenance preset if stamped.

What gets auto-fixed

• Spacing — off-scale gap or scalar padding snaps to the nearest scale value. Array padding is skipped (ambiguous which index).
• Consistency — frames with multiple children but no layout get layout: "vertical".
• Color — recoverable WCAG contrast failures get color: "#000000" or "#FFFFFF", whichever wins against the resolved background. Failures so bad that neither black nor white meets the threshold are not auto-fixed (the background also needs to change).
• Cliché — a known-default purple/indigo accent (#6366f1 and friends) written literally on a node swaps to a neutral accent; a dedicated fake-chrome strip (a row that is just traffic-light dots) gets a D(...) delete. Taste-dependent tells (gradient/glow overuse, the hanging header, fabricated copy) are reported by canvas_evaluate with a suggestion but carry no auto-fix op.

Return shape

{
  "totalIssues": 18,
  "fixableCount": 5,
  "fixes": [
    {
      "nodeId": "abc123",
      "category": "color",
      "op": "U(\"abc123\", { color: \"#000000\" })",
      "rationale": "Switch text color to #000000 for WCAG AA contrast against #F8FAFC",
      "message": "Text \"Sign In\" has contrast ratio 2.8:1 against #F8FAFC. WCAG AA requires 4.5:1."
    }
  ]
}

Apply the ops by joining them with newlines and passing to batch_design, then re-evaluate.

canvas_revise

Closes the critique loop (Phase 13). Judges the canvas against the rubric; if any axis is below the floor, asks an LLM for targeted batch_design ops that raise the failing axes, applies them, re-renders, and re-judges — up to maxIterations passes. Mutates the canvas. Opt-in and bounded; it never runs implicitly.

Param	Type	Description
canvasId	string	Canvas to revise
maxIterations	number?	Revise passes, 1–3 (default 1)
floor	number?	Per-axis rubric floor 1–5 (default 3 / FRAMESMITH_CRITIQUE_FLOOR)
provider	"anthropic" | "openai"?	Force an LLM provider (default auto-detect)

Loop & safety

• Each pass: render → judge → if needsRevision, revise the failing axes → apply (validated through batch_design) → re-render → re-judge.
• Stops when the canvas passes (passed), at the cap (max-iterations), when a pass doesn't improve the overall (no-improvement — the regressing edit is reverted), when the reviser returns nothing (no-ops), or when an op fails to apply (apply-error — the partial edit is reverted).
• Every accepted pass re-stamps metadata.critique + the build log. Costs ≥2 paid API calls per pass (one judge + one revise) and renders between passes (Chrome required).

Return shape

{
  "iterations": [
    { "pass": 1, "overallBefore": 72, "failingAxes": ["variety"],
      "opsApplied": "U(\"cards\", { ... })", "overallAfter": 84 }
  ],
  "finalVerdict": { "rubric": { "...": {} }, "score": 84, "needsRevision": false, "failingAxes": [] },
  "stoppedReason": "passed"
}

Resources

• framesmith://guidelines — markdown authoring guide: width strategies (fixed / percentage / fluid+cap / floor / fit-content), responsive hint semantics (stack / wrap / fixed), common patterns (pricing tiers, two-column hero, tag list, toolbar), and anti-patterns. Source: docs/GUIDELINES.md.

Benchmark

npm run bench runs canvas_evaluate over a fixed corpus of canvases (a high-quality dashboard hero, a minimal well-formed canvas, an intentional-contrast-failure canvas) and diffs the result against benchmark/baselines.json. Catches drift in scoring across renderer / evaluator changes — exit code is nonzero on any score, issue-count, or issue-message change. Re-baseline with npx tsx benchmark/run.ts --update after intentional evaluator rewrites.

Gradients

Nodes support linear and radial gradients via the gradient property:

# Linear gradient (angle in degrees)
I("parent", { type: "frame", width: 400, height: 200, gradient: { type: "linear", angle: 135, stops: [{color: "#667eea", position: 0}, {color: "#764ba2", position: 100}] } })

# Radial gradient
I("parent", { type: "frame", width: 200, height: 200, gradient: { type: "radial", stops: [{color: "#fff", position: 0}, {color: "#000", position: 100}] } })

When gradient is set, it takes precedence over fill. Both can coexist (fill as fallback).

Shadows & Blur

Structured shadows, blur filters, and backdrop blur:

# Structured shadow (supports multiple shadows)
I("parent", { type: "frame", fill: "#fff", shadows: [{x: 0, y: 4, blur: 12, spread: 0, color: "rgba(0,0,0,0.15)"}] })

# Blur filter
I("parent", { type: "frame", fill: "#3b82f6", blur: 4 })

# Backdrop blur (single-function shorthand for `blur`)
I("parent", { type: "frame", fill: "rgba(255,255,255,0.5)", backdropBlur: 8 })

# Glassmorphism (composable backdrop-filter: blur + saturate + brightness + contrast)
I("parent", {
  type: "frame",
  fill: "rgba(255, 255, 255, 0.4)",
  backdropFilter: { blur: 12, saturate: 180, brightness: 110 }
})

The structured backdropFilter form takes precedence over backdropBlur when both are set. The renderer also emits the -webkit-backdrop-filter prefix so glass effects render in Safari/iOS without extra work.

The legacy shadow string property still works for simple cases.

Icons

1,900+ icons from Lucide are available via the icon node type:

I("parent", { type: "icon", icon: "search", iconSize: 24, iconColor: "#888" })
I("parent", { type: "icon", icon: "heart", iconSize: 32, iconColor: "#ef4444" })

Icons render as inline SVGs with configurable size and color.

SVG Paths

For custom shapes and brand marks beyond the Lucide library, use the path node type with a raw SVG d attribute:

I("parent", { type: "path", width: 24, height: 24,
  d: "M 12 2 L 22 22 L 2 22 Z", fill: "#f59e0b" })

# With stroke + viewBox (defaults to `0 0 width height`)
I("parent", { type: "path", width: 48, height: 48, viewBox: "0 0 24 24",
  d: "M 12 2 L 22 22 L 2 22 Z",
  fill: "none", stroke: "#000", strokeWidth: 2,
  strokeLinecap: "round", strokeLinejoin: "round" })

fill/stroke/strokeWidth apply to the path itself (not the wrapper). d and viewBox are validated for safe characters — anything that could break out of the attribute is rejected.

Animations & Transitions

Reference a built-in keyframe to make a node animate in on page load. The renderer auto-emits the @keyframes block only when referenced.

I("hero", { type: "frame", animation: { name: "fadeIn", duration: 400 } })
I("title", { type: "text", animation: { name: "slideUp", duration: 300, delay: 100 } })

Built-in keyframe names: fadeIn, slideUp, slideDown, scaleIn. All end at the natural resting state with animation-fill-mode: both, so the start state applies pre-animation and the end state sticks after.

animation: { name, duration?: 300ms, delay?: 0ms, easing?: "ease-out", iteration?: 1 | "infinite" }. Easing is whitelisted: ease, ease-in, ease-out, ease-in-out, linear (anything else falls back to ease-out).

transition: { property?: "all", duration, easing?: "ease", delay?: 0ms }. Transitions only fire on state change, so they're inert until interactive states exist in the renderer — included today so a future hover/focus PR has a place to land.

Components

Define reusable components and create instances with overrides:

# Define a component (a frame subtree that gets registered)
card=I("document", { type: "component", name: "Card", width: 300, fill: "#1a1a1a", cornerRadius: 12, layout: "vertical", padding: 16, gap: 8 })
I(card, { type: "text", name: "title", content: "Default Title", fontSize: 20, color: "#fff" })
I(card, { type: "text", name: "subtitle", content: "Default subtitle", fontSize: 14, color: "#888" })

# Create instances with overrides (matched by child name)
I("document", { type: "instance", componentId: card, overrides: { title: { content: "My Card" }, subtitle: { content: "Custom text" } } })

Usage Example

Here's a complete session building a login card:

1. Create a canvas and set design tokens

canvas_create({ name: "Login" })
→ {
    "canvasId": "abc123",
    "rootId": "xyz789",
    "name": "Login",
    "projectId": "default-project",
    "viewerUrl": "http://localhost:3001/canvas/abc123",
    "galleryUrl": "http://localhost:3001"
  }

set_variables({
  canvasId: "abc123",
  variables: {
    colors: { bg: "#0a0a0a", surface: "#1a1a2e", accent: "#e94560", text: "#ffffff" },
    spacing: { sm: 8, md: 16, lg: 24, xl: 32 },
    radius: { md: 8, lg: 16 }
  }
})

2. Build the layout with batch_design

batch_design({
  canvasId: "abc123",
  operations: `
    page=I("document", { type: "frame", width: 1440, height: 900, fill: "$bg", layout: "vertical", alignItems: "center", justifyContent: "center" })
    card=I(page, { type: "frame", width: 400, fill: "$surface", cornerRadius: "$lg", padding: [32, 32, 32, 32], layout: "vertical", gap: 24 })
    I(card, { type: "text", content: "Sign In", fontSize: 28, fontWeight: 700, color: "$text" })
    I(card, { type: "frame", width: "100%", height: 44, fill: "#ffffff10", cornerRadius: "$md", padding: [0, 16, 0, 16], layout: "horizontal", alignItems: "center" })
    I(card, { type: "frame", width: "100%", height: 44, fill: "#ffffff10", cornerRadius: "$md", padding: [0, 16, 0, 16], layout: "horizontal", alignItems: "center" })
    btn=I(card, { type: "frame", width: "100%", height: 44, fill: "$accent", cornerRadius: "$md", layout: "horizontal", alignItems: "center", justifyContent: "center" })
    I(btn, { type: "text", content: "Continue", fontSize: 16, fontWeight: 600, color: "$text" })
  `
})

3. Take a screenshot to see the result

screenshot({ canvasId: "abc123" })
→ returns base64 PNG image

4. Iterate — update the button color and verify

batch_design({
  canvasId: "abc123",
  operations: `U("btn-id", { fill: "#3b82f6" })`
})

screenshot({ canvasId: "abc123" })

Running the viewer

The viewer runs in one of two modes — embedded (auto-starts inside the MCP server process) or standalone (long-lived in its own terminal). Standalone is recommended; the embedded mode stops the moment your MCP session ends, so any viewer URL you shared becomes unreachable.

Standalone (recommended)

# In a separate terminal tab — stays alive independently of any MCP session
npx -p framesmith framesmith-viewer

# Or on a specific port
npx -p framesmith framesmith-viewer 3004

Working from a clone instead of npm? Run npm run viewer (or npm run viewer -- 3004) from the repo root — same standalone viewer, run from source.

The standalone viewer:

• Persists across sessions — URLs keep working after Claude / Cursor / Windsurf finishes
• Shared across projects — multiple MCP sessions (from different projects) all use the same viewer
• Auto-detects new canvases — watches ~/.framesmith/canvases/ for changes and picks them up immediately
• Auto-detected by MCP — when the MCP server starts, it probes for a running standalone viewer and uses it instead of starting its own

Routes & API

• Gallery (/) — browse all canvases as clickable cards with live thumbnails
• Project (/project/:id) — same gallery but scoped to one project
• Archive (/archive) — soft-deleted canvases with restore / permadelete actions
• Canvas detail (/canvas/:id) — full rendered design with responsive viewport buttons (Mobile / Tablet / Desktop), Compare mode, Fit toggle, and JSON inspector
• Raw HTML (/canvas/:id/html) — the rendered HTML for embedding or inspection
• JSON API (/api/canvases, /api/canvas/:id/meta) — programmatic access
• Live auto-refresh — the viewer polls for changes every 2 seconds, so the browser updates automatically as your agent runs batch_design

All canvases persist to ~/.framesmith/canvases/ as JSON files and survive process restarts. Set FRAMESMITH_VIEWER_URL in the MCP server env to point at a viewer running on a non-default port.

Workflow

1. Start the standalone viewer in a terminal tab: npx -p framesmith framesmith-viewer
2. canvas_create → get canvas ID
3. Open the viewer URL in your browser for live preview
4. apply_preset or set_variables → set up design tokens
5. batch_design → build the UI with frames, text, icons, components, gradients
6. Watch the viewer auto-refresh as you design
7. screenshot_responsive → preview at mobile/tablet/desktop sizes
8. canvas_diff → compare before/after changes visually
9. export → save final designs to PNG/PDF files

Development

git clone https://github.com/vicmaster/framesmith.git
cd framesmith
npm install
npm run build

Scripts

Command	What it does
npm run build	Compile TypeScript to dist/. Required before the installed MCP server picks up changes — it loads dist/index.js.
npm run dev	Run the server directly via tsx for local iteration. Does not affect the registered MCP server.
npm run viewer [port]	Start the standalone viewer (default auto-picks from 3001).
npx tsx test-*.ts	Run ad-hoc test scripts at the repo root.

Env vars

Variable	Purpose
FRAMESMITH_VIEWER_URL	Point the MCP server at an external viewer (skips starting an embedded one).
FRAMESMITH_VIEWER_PORT	Override the standalone viewer's port.

Conventions

• ESM only ("type": "module"). Imports in TypeScript source use .js extensions even when the source file is .ts.
• Don't edit dist/ — it's regenerated by tsc.
• New MCP tool? Register it in src/index.ts, document it in the Tools section above, and update VISION.md's phase checklist.

License

MIT — see LICENSE.

Copyright (c) 2026 Victor Velazquez.