framesmith

An open-source MCP server that turns your AI coding agent into a capable UI designer. It gives the agent a visual canvas, a library of vetted design patterns, and a quality bar it must clear before showing you anything — so you review a real, non-slop design in the browser and agree on it before any framework code is written.

Contents: What it does · Capabilities · Viewer · Installation · Tools · Usage Example · Workflow · Development

Above: the framesmith viewer, showing the built-in pattern library — 11 vetted page archetypes an agent starts from, each carrying its live quality score (all 100 here). Workspaces and projects sit in the sidebar; you browse canvases like design files.

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

What framesmith does

Left to itself, an AI agent tends to produce UI that looks AI-generated — generic spacing, no icons, a purple gradient by default, placeholder text that reads like placeholder text. framesmith closes that gap by moving design before code and holding it to a bar:

1. Start from taste, not a blank canvas. The agent stamps one of 11 vetted page patterns (dashboard, auth, pricing, settings, onboarding, and more) — each regression-tested to score > 95 with zero cliché tells across every theme — then adapts it. A blank canvas is where slop comes from; a pattern is a non-slop starting point. (list_structures / apply_structure)
2. Use the whole toolkit — like a real UI does. Real icons (Lucide + Material Symbols), fonts resolved by name, real input controls (toggle / checkbox / radio / select), reusable components, and layered design tokens — never faked with Unicode glyphs or stray ellipses.
3. Evaluate, then self-correct. canvas_evaluate scores the design across six craft categories plus a cliché-tell detector, and returns a READY / NOT READY directive. The agent resolves every warning and tell and only presents once it's READY — polishing to the bar is the agent's job, not yours.
4. Review in the browser, own the output. You browse canvases like design files, with a live quality inspector and design-system panel. Designs persist as open JSON checked into your repo — no proprietary format, no lock-in — and can be re-imported from shipped HTML to keep the design honest.

Capabilities at a glance

Area	What you get
Rendering	Scene graph → HTML/CSS → Puppeteer PNG · responsive breakpoints · gradients, shadows, blur, glassmorphism · SVG paths · animations
Pattern library	11 vetted page archetypes + 5 component scaffolds, all scoring > 95 with zero cliché tells; taxonomy axes + a diversification signal so successive screens vary
Quality & taste	canvas_evaluate (6 categories + cliché tells) with a READY/NOT READY directive · canvas_autofix (mechanical fixes) · optional vision-model rubric critique + canvas_revise
Design systems	Layered $tokens (workspace ▸ project ▸ canvas) · style presets · DESIGN.md import
Primitives	Lucide + Material Symbols icons · Google Fonts by name · real form controls · components with instance overrides
Import from code	canvas_import_html / canvas_import_url — token-mapped, structure-reconstructed · canvas_sync_from_url drift detection
Viewer	Read-only browser gallery + detail view · quality inspector (score, issues, click-to-highlight) · design-system token panel
Open by design	MIT · plain HTML/CSS · open JSON you own in your repo · works with any MCP-compatible client

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 canvas in the detail view with the Quality inspector on the right — the same canvas_evaluate score the agent sees, with per-category bars, the issue list, and a Design-system tab. The toolbar exposes breakpoint previews, Compare, Fit, JSON, and lifecycle actions.

Quality panel. The canvas detail view shows a read-only quality inspector on the right: the heuristic canvas_evaluate score (0–100), per-category bars, and the issue list — each cliché tell with its category · tell badge, severity, and suggestion. Issues that canvas_autofix can resolve carry an auto-fixable tag, and clicking any issue highlights its node in the live preview. Every gallery card also shows a color-coded score badge so weak canvases stand out at a glance. The score matches what your agent sees over MCP (same fast-mode evaluation, genre-relaxed by the canvas's preset) — it's computed for display only and never written back.

Design-system panel. A second inspector tab shows the canvas's effective design tokens — color swatches, type scale, spacing, and radius — resolved through the full workspace ▸ project ▸ canvas inheritance chain. Each section notes its dominant source layer, and any token that overrides it is tagged (canvas / project) so you can see at a glance what a given canvas customized versus inherited.

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, toggle, checkbox, radio, select

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

Use textTransform: "uppercase" for uppercase labels (don't bake casing into content), letterSpacing for tracking, and fontVariationSettings (e.g. '"wght" 650') for variable-font axes.

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

Fonts load by name automatically — naming a fontFamily in a typography token (or on a node) resolves it from Google Fonts at token-write time, with a render-time backstop catching anything else. Binaries are cached under ~/.framesmith/fonts/, so renders are offline and deterministic after the first resolve; typography.body.fontFamily becomes the document default. An unresolvable family renders in the fallback stack and adds a Font warnings item to the screenshot/export result.

set_fonts covers explicit registration. Three forms, combinable:

{
  "families": ["Inter", "JetBrains Mono"],
  "fonts": [
    { "family": "Inter", "url": "https://fonts.googleapis.com/css2?family=Inter:wght@400;700" },
    { "family": "Brand Face", "url": "https://example.com/brand.woff2", "weight": 400 }
  ]
}

• families — resolve by name from Google Fonts and merge into the existing declarations.
• fonts with a Google Fonts CSS URL (fonts.googleapis.com/css2?...) — faces are extracted from the stylesheet automatically.
• fonts with a direct binary URL (.woff2 / .woff / .ttf / .otf or a data: URI) — for non-Google sources.

fonts replaces declarations wholesale (pass [] to clear); families merges. The renderer emits @font-face blocks plus <link rel="preconnect"> per remote origin, with font-display: swap.

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 scaffolds you stamp onto a canvas and then populate. Returns each structure's name, kind, description, and (for pages) 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.

Two kinds:

• page — whole-page scaffolds stamped once at the canvas root: marquee-hero, bento-grid, stat-led, editorial-longform, split-workbench, catalogue, dashboard, auth, pricing, settings, onboarding. 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. Every page scaffold is regression-tested to score > 95 with zero cliché tells across all five presets (the pattern library's taste bar), so it's a non-slop starting point you adapt, not boilerplate.
• component — reusable fragments stamped under any node via targetId, repeatably: data-table (header + 3 rows with avatar/name/email, role chip, status toggle, actions), form-field, toolbar, stat-card, toggle-row. A high-fidelity table costs one stamp instead of ~80 hand-placed nodes.

apply_structure

Stamp a layout structure onto a canvas and return 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.

• Page scaffolds insert at the canvas root (refusing on a non-empty canvas unless replace), record provenance (metadata.provenance), and append to the per-project build log that feeds the diversification signal.
• Component scaffolds insert under targetId (default root), repeatably — every stamp re-keys its node IDs (form-field-1-…, form-field-2-…) and returns an idMap (template ID → live ID) for follow-up ops. Component stamps don't touch provenance or the build log: they don't shape the page.

Param	Type	Description
canvasId	string	Canvas ID
structure	string	Structure name (use list_structures, e.g. "marquee-hero", "data-table")
replace	boolean?	Page scaffolds: if the root already has children, clear them before stamping. Default false (refuses on a non-empty canvas)
targetId	string?	Component scaffolds: node to stamp under (default "document")

canvas_import_html

Import an HTML snippet (+ optional CSS) as an editable canvas — the reverse of export. The markup renders headlessly and a computed-style DOM walk maps it to the scene graph:

Source	→ Scene graph
flex/block container	frame + layout/gap/padding/alignItems/justifyContent/wrap
display: grid	rows of proportional columns from the computed track template (grid-column spans honored — numeric spans win, else the box width decides); irregular templates degrade to a stack with a warning. Recorded in report.layout
centered content (margin: auto, max-width, flex-center)	the parent centers (alignItems) and the child keeps its real width — max-width becomes the fluid width: "100%" + maxWidth idiom. Recorded in report.layout
floats / inline-block / unmodeled multi-column CSS	geometry clustering: children's computed boxes group into row bands (≥50% vertical overlap, consistent column counts) → rows of proportional columns. Conservative by design — anything that looks multi-column but doesn't cluster consistently imports as an honest stack with a stack-fallback entry + warning
<table> / <tr> / <td>/<th>	a vertical frame of horizontal row frames with proportional percentage cell widths (from the computed boxes — colspan handled free); thead/tbody unwrap, <caption> becomes a text node, bottom borders become hairline divider frames. Recorded in report.layout
text run	text (size, weight, color, family, line-height, letter-spacing, transform, align)
<img> (absolute/data URL)	image
inline <svg>	icon when the path data matches a bundled Lucide/Material glyph; else path
checkbox / radio / role="switch" / <select>	the input-primitive node types, with live checked/selected state
background / border / radius / shadow / opacity / overflow	fill / stroke+strokeWidth / cornerRadius / shadows / opacity / overflow

Lossy by design. Every import returns a report — counts, warnings (dropped background images, grid containers, truncations), unmatched icons/fonts — and that report is the contract; the goal is an editable, honest starting point, not a pixel-perfect clone. Single-child wrapper divs collapse, same-style text runs merge, invisible nodes drop (all tunable via flatten).

Param	Type	Description
html	string	The snippet to import
css	string?	CSS to apply — e.g. the compiled Tailwind stylesheet. A bare Tailwind snippet has no runtime, so classes render unstyled without this
projectId	string?	Project to create the canvas in (default project if omitted)
name	string?	Canvas name (default "Imported HTML")
selector	string?	Import only the first match within the snippet
width	number?	Container width layouts resolve against (default 1440)
flatten	object?	{ collapseWrappers, mergeTextRuns, dropInvisible, maxDepth }
tokenMatch	object?	{ source: "workspace" | "designMd" | "tailwind" | "none", tolerance?, designMd? } — snap concrete values back to $token refs (default: the target project's merged design system)
tailwind	object?	{ theme: { name: value } } — the project's @theme map; widens which class names map to $tokens

Token re-mapping makes the import a token-driven design instead of a pile of hex:

• Tailwind intent first — class names carry intent a computed value can't: bg-surface → fill: "$surface", gap-4 → 16, rounded-xl → 12, text-sm font-semibold uppercase → typography props. Custom utilities resolve via tailwind.theme; palette classes (bg-red-500) map to the bundled v4 palette as hex literals (generated from the official oklch values by Chrome itself — see scripts/generate-tailwind-palette.ts), so a bare snippet styles without compiled CSS; arbitrary values and unknowns fall through to computed styles. Geometry intent and palette literals only fill gaps the CSS didn't set; token-ref colors override computed literals.
• Nearest-color snapping second — remaining literal colors snap to the matched design system within tolerance (exact matches always; near-ties between two tokens are reported and left literal, never guessed). Spacing/radius/fontSize values that equal a scale token are reported under report.scaleMatches.
• Fonts seen in computed styles feed the font-by-name resolver, so the imported canvas renders in the same faces.

Returns { canvasId, rootId, report } — report.snapped / literals / scaleMatches / warnings are the contract.

canvas_import_url

Import a live page as an editable, token-mapped canvas — point at a running app and the screen becomes the design-of-record without redrawing. Same engine and token re-mapping as canvas_import_html, plus live-page controls:

Param	Type	Description
url	string	The page to import (http/https only)
viewport	object?	{ width, height } — the width layouts resolve against (default 1440×900)
selector	string?	Import one component instead of the whole page (default body)
waitFor	string | number?	CSS selector to await, or a delay in ms — for client-rendered UI
auth	object?	{ headers?, cookies? } for gated pages — used in a throwaway browser context, never persisted to the canvas, provenance, or report
projectId / name / flatten / tokenMatch / tailwind	—	Same as canvas_import_html

Relative image URLs resolve against the page; fonts seen in computed styles load through the font-by-name resolver so the canvas renders in the same faces. The source URL (never auth) is recorded in metadata.provenance.importedFrom.

canvas_sync_from_url

Drift detection — the design-of-record as a living contract. Re-imports a live page ephemerally (no canvas created, nothing mutated) and pixel-diffs it against an existing canvas at the same viewport:

Param	Type	Description
canvasId	string	The canvas that is the design-of-record
url	string	The live page to compare (http/https)
viewport	object?	Compare size (defaults to the canvas root size)
selector / waitFor / auth	—	Same as canvas_import_url (auth in a throwaway context, never persisted)

Returns the diff image (changed regions in red), changePercent, changedPixels/totalPixels, and the import report. Both sides render at scale 1, so the percentage is comparable run-to-run — an unchanged page diffs at ~0%.

CI pattern (a pattern, not a shipped feature): after deploy, call canvas_sync_from_url for each route ↔ canvas pair and fail the job when changePercent exceeds your threshold — design ↔ code divergence becomes a build failure instead of a surprise.

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, per-node actionable issues, and a directive — a present/keep-working verdict. Designed for generator-evaluator loops: build with batch_design, score with canvas_evaluate, fix the issues targeting the returned nodeIds, repeat until the directive says READY.

The directive is the operating contract that keeps unfinished work off the user's screen. It reads READY TO PRESENT only when the score is > 95 and there are zero warnings and zero cliché tells; otherwise NOT READY with what to resolve. (Cliché tells block even at info severity — they're the slop signal; pure advisories like "consider extracting components" are optional.) Resolve everything and re-evaluate until it says READY before showing the design to the user.

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, eyebrow rhythm (an eyebrow above nearly every section), slop copy (stock AI phrasing — filler verbs, scroll cues, placeholder names, hype labels), radius consistency (too many distinct corner radii), pure black/white (#000000 ink / #ffffff page vs off-black/off-white), accent consistency (multiple competing accent hues). 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",
  "directive": "NOT READY — 87/100 with 1 issue(s) to resolve. Fix them now: canvas_autofix for the mechanical subset, batch_design for the rest, then re-run canvas_evaluate. Repeat until there are zero warnings/cliché tells and the score is > 95. Do NOT show this design to the user yet."
}

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; pure-black ink (#000000 text/icon/stroke) softens to off-black. Taste-dependent tells (gradient/glow overuse, the hanging header, fabricated copy, eyebrow rhythm, slop copy, mixed radius systems, competing accents) 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

Two bundled sets are available via the icon node type, rendering as inline SVGs with configurable size and color:

Lucide (1,900+, stroke style) — unprefixed names, browse here:

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

Material Symbols (3,800+, fill style) — material: prefix, browse here:

I("parent", { type: "icon", icon: "material:check", iconSize: 24, iconColor: "#b71421" })
I("parent", { type: "icon", icon: "material:settings", iconStyle: "rounded" })
I("parent", { type: "icon", icon: "material:star-fill" })   # "-fill" suffix = filled variant

iconStyle picks the Material variant ("outlined" default, "rounded", "sharp"); it's ignored for Lucide.

Input controls

toggle, checkbox, radio, and select are first-class node types — static renders with a checked / value / disabled state, so app UI doesn't have to be faked from frames and ellipses:

I("parent", { type: "toggle", checked: true })
I("parent", { type: "checkbox", checked: true })
I("parent", { type: "radio" })
I("parent", { type: "select", value: "Administrator", width: 220 })
I("parent", { type: "select" })                      # renders a muted "Select…" placeholder
I("parent", { type: "toggle", checked: true, disabled: true })   # 50% opacity

Colors default from the design system — $accent (falling back to $primary) for active states, $border for outlines, $bg-surface / $text-primary for the select — with neutral fallbacks on unthemed canvases. Explicit fill / stroke / color override. Defaults: toggle 44×24, checkbox/radio 18×18, select fit-content (give it a width for form layouts).

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

A complete session designing a sign-in screen — the framesmith way: start from a pattern, adapt it, and let the evaluator gate the result (rather than building from a blank canvas and faking controls out of frames).

1. Start from a vetted pattern, not a blank canvas

canvas_create({ name: "Sign in" })
→ { "canvasId": "abc123", "viewerUrl": "http://localhost:3001/canvas/abc123", ... }

apply_structure({ canvasId: "abc123", structure: "auth" })
→ returns the placeholder node IDs to populate (au-title, au-sub, au-email, au-password, au-submit, ...)

The auth pattern already scores > 95 — a centered card with real form fields, a real submit button, honest placeholder copy, and an accent that isn't the default purple. You're adapting a good design, not inventing one.

2. Adapt it — set the brand accent and the copy

project_set_design_system({ projectId: "default-project", variables: { colors: { accent: "#2563EB" } } })

batch_design({
  canvasId: "abc123",
  operations: `
    U("au-title", { content: "Welcome back" })
    U("au-sub", { content: "Sign in to continue to your workspace." })
  `
})

3. Evaluate — and only present when the directive says READY

canvas_evaluate({ canvasId: "abc123", mode: "fast" })
→ {
    "overallScore": 98,
    "issues": [],
    "directive": "READY TO PRESENT — 98/100, no blocking issues."
  }

If it came back NOT READY, you'd apply canvas_autofix (mechanical fixes) / batch_design (the rest) and re-evaluate until it clears — then screenshot and share the viewer URL. The directive is what keeps an unfinished design off the user's screen.

4. Verify across breakpoints

screenshot_responsive({ canvasId: "abc123" })   // renders mobile / tablet / desktop

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

The loop framesmith is built around — start from taste, adapt, and polish to the bar before anyone sees it:

1. Start the standalone viewer in a terminal tab: npx -p framesmith framesmith-viewer, and open its URL for live preview.
2. canvas_create → get a canvas ID (share the viewer URL).
3. Set the design system once — workspace_set_design_system / apply_preset / set_variables (colors, spacing, radius, typography as $tokens).
4. apply_structure → stamp a vetted page pattern, then adapt it with batch_design (real icons, controls, and components — not faked from frames). This is the starting point; a blank canvas is the slow, sloppy path.
5. Watch the viewer auto-refresh as you design; screenshot to check the render.
6. canvas_evaluate → read the directive. Resolve every warning and cliché tell (canvas_autofix for the mechanical subset, batch_design for the rest), then re-evaluate. Repeat until it says READY — only then present the design.
7. screenshot_responsive → confirm it holds at mobile / tablet / desktop.
8. canvas_diff / canvas_sync_from_url → compare versions, or check the shipped app hasn't drifted from the approved design.
9. export → save final designs to PNG/PDF.

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.
FRAMESMITH_CHROME_PATH	Chrome binary for screenshots/exports (falls back to PUPPETEER_EXECUTABLE_PATH, then the Puppeteer-managed Chrome). Set it in the MCP server's env config — clients often launch servers with a minimal env.

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.