umg-mcp-authoring

UMG MCP Authoring

Use MCP tools as the hands and this skill as the experience. Do not mutate .uasset files directly and do not bypass MCP with raw socket scripts when validating the public protocol.

For the five-system login demo and concrete script workflow, read login-demo.md.

Workflow

1. Set the attention target first with set_target_umg_asset.

   • Passing a missing /Game/... UMG path creates a WidgetBlueprint.
   • Use set_target_widget only when the next operation is intentionally scoped to a widget.
   • Prefer omitted/default path arguments after target is established.

2. Build widget structure with panel parents.

   • CanvasPanel, Overlay, VerticalBox, and HorizontalBox are reliable authoring parents.
   • Current create_widget attaches children through UPanelWidget; do not create children directly under Button or Border.
   • To put text on a button or content over a border, create an Overlay and add the visual widget plus the text as siblings.

3. Write properties as union updates.

   • set_widget_properties should set or overwrite supplied properties and leave unspecified properties intact.
   • Use Slot.Position and Slot.Size aliases for CanvasPanel children when possible.
   • Use nested Slot objects for panel-slot alignment and padding.
   • Use delete_widget only for explicit deletion and pass confirm_delete=true.
   • Prefer apply_layout for bulk layout authoring; export_umg_to_json and apply_json_to_umg are hidden compatibility/debug paths.

4. Use HLSL materials for UI visual richness.

   • Prefer hlsl_set_target, hlsl_set, and hlsl_compile.
   • New HLSL targets default to UI material behavior.
   • For detailed material rules, use the umg-material-mcp skill.

5. Animate widgets through Sequencer.

   • Create or select an animation with create_animation and set_animation_scope.
   • Focus the animated widget with set_target_widget or set_widget_scope.
   • Use animation_append_widget_tracks for widget-oriented union key writes.
   • Use animation_append_time_slice when authoring a single moment across one or more widgets.
   • Read back with animation_overview or animation_time_properties; do not trust write responses alone.
   • Treat get_animation_keyframes, get_animation_full_data, set_property_keys, remove_property_track, and remove_keys as hidden compatibility commands, not default authoring tools.