platform-widget-generate

name: platform-widget-generate description: "Use this skill to author a complete HXL WidgetBundle (UEM body + schema.json + -meta.xml). TRIGGER when: user asks for a widget, mosaic, fragment, card, or rich UI surface for any subject, domain, feature, or entity noun; the prompt names only an entity or data shape without invoking Lightning Types, CLTs, or Apex-backed types. DO NOT TRIGGER when: the prompt explicitly says 'Lightning Type', 'CLT', 'Custom Lightning Type', 'Apex-backed type', or references '@apexClassType/...' (use platform-lightning-type-widget-coordinate); authoring a custom-LWC renderer for a Custom Lightning Type (use platform-custom-lightning-type-generate); or editing only an LWC component." metadata: version: "1.4" domains: ["Platform", "Agentforce"] minApiVersion: "68.0" relatedSkills: - "platform-apex-generate" - "platform-custom-lightning-type-generate" - "platform-lightning-type-widget-coordinate" mcpTools: metadata-experts: tools: ["execute_metadata_action"] semver: ">=1.0.0"

Generating a Widget Bundle

Author a complete WidgetBundle: a UEM tree (tile/widget), a JSON Schema describing the widget's input contract, and the .uiwidget-meta.xml that registers the bundle.

When to Use This Skill

Use when the user asks for a widget, mosaic, fragment, or card-style rich UI surface. Do not use this skill for custom-LWC renderers or for renderer.json files inside a Custom Lightning Type bundle — those belong to platform-custom-lightning-type-generate.

Inputs

• widgetName (required) — camelCase identifier; becomes the directory name under uiWidgets/.
• A shape — what data the widget renders. The widget cannot be generated without it. The shape arrives one of two ways, in priority order:
  1. lightningTypeSchema — { path, apexClassFqn } for an existing Apex-backed Lightning Type. The FQN takes one of two forms: outer-class (<namespace>__<ClassName>) where the outer class is the payload, or inner-class (<namespace>__<ClassName>$<InnerClass>) where the named inner class is the payload. Passed in by the platform-lightning-type-widget-coordinate orchestrator. When present, derive per references/schema-from-lightning-type.md.
  2. Extracted from the user's prompt — when no lightningTypeSchema is passed, infer the shape directly from what the user wrote: a pasted JSON payload, an enumerated field list ("id as string, total as number"), or descriptive prose. The output is the same ordered list of { name, type, required } either way.

If neither source yields a shape, STOP and ask the user before proceeding.

Output

Three files in <pkgDir>/uiWidgets/<widgetName>/:

See references/widget-bundle-layout.md for the <pkgDir> resolution procedure and the exact <widgetName>.uiwidget-meta.xml shape.

Composition

A widget body is a UEM tree of blocks nested under contentBody.widgetBody. The root node is tile/widget. Every node — root and non-root — has the same shape: no type key; just definition, optional attributes, optional meta, and optional children. Block shape:

interface Block {
  definition: string  // {namespace}/{blockName} — root is "tile/widget"
  attributes?: Record<string, any>
  meta?: { // see references/widget-meta-directives.md
    forEach?: string
    forItem?: string
    if?: string
  }
  children?: Block[]
}

The first child of tile/widget.children SHOULD be a single tile/column. All widget content typically goes inside that first child for predictable vertical structure across surfaces.

Available Metadata Actions

discoverUiComponents

Purpose: Discover the palette of blocks available for composition.

Required parameters: actionName: "discoverUiComponents", metadataType: "FRAGMENT", parameters.pageType: "FRAGMENT". Optional: searchQuery to filter by name/description.

Returns: list of { definition, description, label, attributes? }.

getUiComponentSchemas

Purpose: Fetch JSON schemas (property types, required vs optional, validation) for selected blocks.

Required parameters: actionName: "getUiComponentSchemas", metadataType: "FRAGMENT", parameters.pageType: "FRAGMENT", parameters.componentDefinitions: ["namespace/definition", ...]. Optional: includeKnowledge (default true).

Returns: componentSchemas[] — success entries carry the JSON schema, failure entries carry an error message. Partial failures are supported.

Never pass tile/widget to getUiComponentSchemas — it is a fixed wrapper, not a queryable component.

Attribute Binding

• Bind a block property to runtime data with {!$attrs.<attrName>}. <attrName> MUST match a property name in schema.json.
• Inside a forEach, reference the loop variable instead — e.g. "text": "{!$item.name}". See references/widget-meta-directives.md.
• A binding may be a formula expression instead of a bare field reference. See references/widget-formulas.md for the full supported-function list, syntax, and gotchas.

Actions

tile/button supports an actions attribute that dispatches an action node on an event. Two action definitions are supported:

{
  "definition": "tile/button",
  "attributes": {
    "label": "Button Label",
    "variant": "primary",
    "actions": { "click": [ { "definition": "action/sendMessage", "attributes": { "content": "content" } } ] }
  }
}

{
   "definition": "tile/button",
   "attributes": {
      "label": "Button Label",
      "variant": "primary",
      "actions": { "click": [ { "definition": "action/openLink", "attributes": { "url": "https://www.example.com", "target": "_blank" } } ] }
   }
}

A tile/button with no actions attribute renders disabled — a button exists to trigger an action, so always attach a click action to a button meant to be interactive.

Layout Best Practices

These conventions cover widget structure — how blocks are grouped and stacked.

• Nesting: Prefer flat layouts. Only nest a tile/column inside a tile/row (or vice versa) when the visual orientation actually changes for that subgroup.
• Authoritative palette: the table above lists typical layout primitives. Always confirm a block exists by inspecting discoverUiComponents output — do not assume a block name from this table without seeing it in the discovery response.

Styling Best Practices

Widgets express intent, not pixels. Each surface provides a default look and feel; brand/theme overrides apply automatically.

• Style semantically. Use variant, size, and other enum-typed attributes (primary, destructive, success, warning). Do not pin literal colors or pixel values.
• One primary action per visible group. At most one tile/button with variant: primary. Use secondary or destructive for additional actions (see the tile/button schema for the full variant enum).
• Every tile/button needs a click action. See Actions above — an action-less button renders disabled.
• One h1 per widget. Use h2/h3 for sub-section headings, body for prose, caption for helper text.
• Use semantic state variants on state-bearing blocks (tile/badge, tile/callout).
• Accept schema defaults for gap, size unless there is a specific reason to override.
• Don't pin width unless a content constraint requires it.
• Use the Lucide icon set. Pass the Lucide name ("check", "alert-circle"); other icon libraries are not supported.

Workflow

1. Resolve the widget spec — an ordered list of { name, type, required }. Source depends on which input was provided (see Inputs):

   • If lightningTypeSchema was passed by the orchestrator → derive per references/schema-from-lightning-type.md.
   • Otherwise → infer the list directly from the user prompt (pasted JSON payload, enumerated field list, or descriptive prose).

2. Discover blocks (REQUIRED — do NOT skip). Call the discoverUiComponents metadata action via execute_metadata_action. Use property types from the widget spec to seed searchQuery (text → "text", number → "number"). If discoverUiComponents returns success: false, an error, or an empty list, STOP and surface the error verbatim — do not improvise block names from memory, prior runs, or training data. Re-run discover with a different searchQuery only if the failure is search-query-specific.

3. Select blocks. Choose one block per widget-spec property, plus structural primitives from Layout Best Practices.

4. Get block schemas (REQUIRED — do NOT skip). Call the getUiComponentSchemas metadata action via execute_metadata_action for the selected blocks. Review property metadata. If componentSchemas returns all-failure or empty, STOP and surface the error — do not improvise from existing widgets in the project.

5. Build the UEM tree (example reads REQUIRED — do NOT skip). First, identify which patterns match the widget spec and read each matching example file from this skill's own examples/ directory (<skill-root>/examples/):

   Pattern in the spec	Example to read
   Single object (no iteration)	<skill-root>/examples/single-object.json
   Any list iteration (root-level array, nested list, or list embedded in a single-object widget)	<skill-root>/examples/list-with-foreach.json
   Conditional rendering (if bound to a boolean or formula)	<skill-root>/examples/conditional.json
   Computed values, text/number transforms, or if driven by a formula (not a bare boolean field)	<skill-root>/examples/formulas.json

   A spec may match multiple patterns (e.g. a list of items where some items render conditionally reads both list-with-foreach.json and conditional.json). Read every matching example, and only those — do not skip the read because the pattern feels familiar.

   Before writing any formula, read references/widget-formulas.md in full — it is the authoritative list of supported operators and functions; do not improvise a function name or operator that isn't documented there.

   Then:

   • Map each widget-spec property to a block property; preserve spec order.
   • Decide root iteration: single object → properties directly under root tile/column. Collection → wrap repeating block in forEach/forItem. See references/widget-meta-directives.md.
   • Bind values with {!$attrs.X} (or {!$item.X} inside forEach).
   • For conditional blocks, add "if" on meta — either a bare lightning__booleanType property, or a formula expression that evaluates to boolean. See references/widget-formulas.md.
   • When the widget spec calls for a computed value (a total, a derived label, a formatted string) rather than a raw field, express it as a formula inside {!...} per references/widget-formulas.md — do not invent a new schema property to hold a value that can be computed from existing ones.

6. Author schema.json. Build the JSON Schema from the widget spec. Fields live one level deep under an attributes wrapper:

   {
     "title": "<Widget Display Name>",
     "description": "<one line about what the widget shows>",
     "type": "object",
     "properties": {
       "attributes": {
         "lightning:type": "lightning__objectType",
         "properties": {
           "<propertyName>": {
             "title": "<label>",
             "description": "<short description>",
             "lightning:type": "<lightning__textType | lightning__numberType | ...>"
           }
         }
       }
     }
   }
   

   Required root keys: title, type: "object", properties.attributes (with lightning:type: "lightning__objectType" and a nested properties map). See references/schema-from-lightning-type.md for full primitive type guidance.

7. Author <widgetName>.uiwidget-meta.xml. See references/widget-bundle-layout.md for the exact shape.

8. Resolve <pkgDir> and write the bundle. Follow the procedure in references/widget-bundle-layout.md (## Resolving <pkgDir>). A widget bundle is a three-file set — all three files must be written in the same step; a bundle with fewer than three files is incomplete and will not deploy.

   <pkgDir>/uiWidgets/<widgetName>/<widgetName>.json               # widget envelope — UEM tree (primary artifact)
   <pkgDir>/uiWidgets/<widgetName>/schema.json                     # attribute contract for the envelope
   <pkgDir>/uiWidgets/<widgetName>/<widgetName>.uiwidget-meta.xml  # UiWidgetBundle registration
   

   Each file has a distinct role:

   • <widgetName>.json — the widget envelope with the tile/widget UEM tree. This is the primary artifact; schema.json is its companion contract, not a substitute.
   • schema.json — the JSON Schema for the attributes referenced by {!$attrs.X} bindings in the envelope.
   • <widgetName>.uiwidget-meta.xml — the UiWidgetBundle element that registers the bundle for source tracking and deployment.

   Write all three before proceeding to self-validation.

9. Self-validate. Before reporting, confirm each check below and report each result individually (pass or fail (<reason>)). Do not summarize as a single "all passed" line — list every check so a reviewer can spot a silent skip.

   • schema-parses — <pkgDir>/uiWidgets/<widgetName>/schema.json parses as JSON.
   • schema-root-keys — root has title (string), type: "object", and properties.attributes (object) — where properties.attributes carries lightning:type: "lightning__objectType" and a nested properties map. No unevaluatedProperties: false.
   • schema-leaf-types — every leaf under properties.attributes.properties carries a lightning:type. Singular nested inner-class fields carry lightning:type set to the inner Apex class reference (@apexClassType/<namespace>__<OuterClass>$<InnerClass>); the nested shape is not redeclared. List<InnerClass> fields carry lightning:type: "lightning__listType" with items.lightning:type set to the inner Apex class reference (@apexClassType/<namespace>__<OuterClass>$<InnerClass>), not a redeclared field map — see references/schema-from-lightning-type.md. When the list has no Apex-backed type (schema inferred from the prompt), items.lightning:type: "lightning__objectType" MUST carry an inline nested properties map for every item field the body binds via {!$item.X}.
   • bindings-resolve — every {!$attrs.X} (or {!$attrs.<outerField>.<innerField>} for nested objects) in <widgetName>.json resolves to a property under schema.json properties.attributes.properties, and every {!$item.X} resolves to a forItem loop variable defined upstream. This applies to $attrs/$item references inside formula expressions too.
   • formulas-supported — every function name used inside a {!...} expression appears in the Supported functions list in references/widget-formulas.md.
   • body-envelope — <widgetName>.json root has type: "lightning__agentforceWidget" and a contentBody object whose widgetBody carries the UEM tree rooted at tile/widget. No node in the tree — root or non-root — carries a type key.
   • metaxml-wellformed — <widgetName>.uiwidget-meta.xml parses as well-formed XML.
   • metaxml-elements — <widgetName>.uiwidget-meta.xml has root <UiWidgetBundle> and contains <masterLabel> (non-empty), <description> (non-empty), and <widgetType>JSON</widgetType>.
   • files-present — all three files exist at the resolved <pkgDir>/uiWidgets/<widgetName>/ path.
   • button-actions-present — every tile/button in <widgetName>.json has an actions.click action node whose definition is action/openLink or action/sendMessage.

Rules / Constraints

Gotchas

Reference File Index