JSON Render UI

Overview

Transform natural language UI requests into working dashboards and applications. Claude acts as the translation layer (prompt → JSON), the skill provides the rendering runtime (JSON → UI).

Architecture:

User prompt → Claude (constrained by catalog) → UITree JSON → Preact renderer → UI

Output Format

Claude emits a UITree structure:

{
  "root": "main",
  "elements": {
    "main": {
      "key": "main",
      "type": "Grid",
      "props": { "columns": 2, "gap": "md" },
      "children": ["metric1", "metric2"]
    },
    "metric1": {
      "key": "metric1",
      "type": "Metric",
      "props": {
        "label": "Revenue",
        "valuePath": "/revenue",
        "format": "currency"
      }
    },
    "metric2": {
      "key": "metric2",
      "type": "Metric",
      "props": {
        "label": "Growth",
        "valuePath": "/growth",
        "format": "percent"
      }
    }
  },
  "data": {
    "revenue": 125000,
    "growth": 0.15
  }
}

Component Catalog

Claude can ONLY use these components. This is the guardrail.

Layout Components

Component	Props	Children	Description
Card	title?, description?, padding?: sm|md|lg	Yes	Container with optional header
Grid	columns?: 1-4, gap?: sm|md|lg	Yes	CSS grid layout
Stack	direction?: horizontal|vertical, gap?: sm|md|lg, align?: start|center|end|stretch	Yes	Flexbox stack

Data Display

Component	Props	Children	Description
Metric	label, valuePath, format?: number|currency|percent, trend?: up|down|neutral, trendValue?	No	Single KPI display
Chart	type: bar|line|pie|area, dataPath, title?, height?	No	Data visualization
Table	dataPath, columns: [{key, label, format?: text|currency|date|badge}]	No	Tabular data
List	dataPath, emptyMessage?	Yes	Rendered list from array

Interactive

Component	Props	Children	Description
Button	label, action, variant?: primary|secondary|danger|ghost, size?: sm|md|lg, disabled?	No	Clickable action
Select	label?, bindPath, options: [{value, label}], placeholder?	No	Dropdown select
DatePicker	label?, bindPath, placeholder?	No	Date input

Typography

Component	Props	Children	Description
Heading	text, level?: h1|h2|h3|h4	No	Section heading
Text	content, variant?: body|caption|label, color?: default|muted|success|warning|danger	No	Text paragraph

Status

Component	Props	Children	Description
Badge	text, variant?: default|success|warning|danger|info	No	Status indicator
Alert	type: info|success|warning|error, title, message?, dismissible?	No	Notification banner

Special

Component	Props	Children	Description
Divider	label?	No	Visual separator
Empty	title, description?, action?, actionLabel?	No	Empty state

Data Binding

Props ending in Path (e.g., valuePath, dataPath, bindPath) reference the data model using JSON Pointer syntax:

• /revenue → data.revenue
• /users/0/name → data.users[0].name
• /filters/dateRange → data.filters.dateRange

Visibility Conditions

Any element can have a visible property:

{
  "type": "Alert",
  "props": { "type": "error", "title": "Error" },
  "visible": { "path": "/hasError" }
}

Visibility expressions:

• true / false — Static
• { "path": "/some/path" } — Truthy check
• { "and": [...] } — All conditions true
• { "or": [...] } — Any condition true
• { "not": {...} } — Negation
• { "eq": [a, b] } — Equality

Generating Output

Step 1: Emit UITree JSON

Analyze the user's request and emit a UITree structure. Include sample data that matches the schema.

Step 2: Create Artifact

Create an HTML artifact that:

1. Embeds the UITree JSON
2. Renders the UI

Start from assets/template.html, which already carries the embedded renderer — there is no separate renderer.js to inline.

Constraints

DO:

• Use only catalog components
• Provide realistic sample data
• Use semantic component choices (Metric for KPIs, Table for tabular data)
• Keep trees flat (no deep nesting beyond 3 levels)

DO NOT:

• Invent new component types
• Use arbitrary HTML/CSS
• Omit required props
• Create deeply nested structures

Example

User: "Create a sales dashboard with revenue, orders, and a chart showing monthly trends"

Claude outputs:

{
  "root": "dashboard",
  "elements": {
    "dashboard": {
      "key": "dashboard",
      "type": "Stack",
      "props": { "direction": "vertical", "gap": "lg" },
      "children": ["header", "metrics", "chartCard"]
    },
    "header": {
      "key": "header",
      "type": "Heading",
      "props": { "text": "Sales Dashboard", "level": "h1" }
    },
    "metrics": {
      "key": "metrics",
      "type": "Grid",
      "props": { "columns": 3, "gap": "md" },
      "children": ["revenue", "orders", "avgOrder"]
    },
    "revenue": {
      "key": "revenue",
      "type": "Card",
      "props": { "padding": "md" },
      "children": ["revenueMetric"]
    },
    "revenueMetric": {
      "key": "revenueMetric",
      "type": "Metric",
      "props": {
        "label": "Total Revenue",
        "valuePath": "/revenue",
        "format": "currency",
        "trend": "up",
        "trendValue": "12%"
      }
    },
    "orders": {
      "key": "orders",
      "type": "Card",
      "props": { "padding": "md" },
      "children": ["ordersMetric"]
    },
    "ordersMetric": {
      "key": "ordersMetric",
      "type": "Metric",
      "props": {
        "label": "Orders",
        "valuePath": "/orders",
        "format": "number"
      }
    },
    "avgOrder": {
      "key": "avgOrder",
      "type": "Card",
      "props": { "padding": "md" },
      "children": ["avgMetric"]
    },
    "avgMetric": {
      "key": "avgMetric",
      "type": "Metric",
      "props": {
        "label": "Avg Order Value",
        "valuePath": "/avgOrderValue",
        "format": "currency"
      }
    },
    "chartCard": {
      "key": "chartCard",
      "type": "Card",
      "props": { "title": "Monthly Trends", "padding": "md" },
      "children": ["chart"]
    },
    "chart": {
      "key": "chart",
      "type": "Chart",
      "props": {
        "type": "line",
        "dataPath": "/monthlyData",
        "height": 300
      }
    }
  },
  "data": {
    "revenue": 284500,
    "orders": 1247,
    "avgOrderValue": 228,
    "monthlyData": [
      { "month": "Jan", "value": 18000 },
      { "month": "Feb", "value": 22000 },
      { "month": "Mar", "value": 28000 },
      { "month": "Apr", "value": 24000 },
      { "month": "May", "value": 32000 }
    ]
  }
}

Then wrap in the artifact template from assets/template.html.

Files

• assets/template.html — Complete artifact template with embedded renderer
• assets/catalog.json — Machine-readable component schemas
• references/uitree-format.md — Detailed UITree specification