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play_widget_animation

Destructive

Triggers a Widget Blueprint animation in Unreal Engine, using live PIE playback when an active widget instance exists and returning a headless status otherwise.

Instructions

Play a widget animation. REAL playback (UUserWidget::PlayAnimation) when a live PIE instance of this WidgetBP is found in the viewport's active UUserWidgets; falls back to an honest headless gate (played:false, headless:true, requires_pie:true) when no PIE session is running or no live instance is found.

Returns: { widget_bp_path: string, animation_name: string, animation_exists: bool, played: bool, headless: bool, requires_pie: bool, note: string, saved: bool, live_widget_name?: string, live_animation_name?: string, world: string, world_name: string|null, world_package: string|null, world_type: string|null, net_mode: string|null, pie_instance: number }

Input Schema

TableJSON Schema
NameRequiredDescriptionDefault
worldNoOptional world selector: absent/'pie' (default: PlayWorld, else the first PIE context) | 'server' (the PIE world with authority) | 'client' | 'pie:N' | 'game' (alias of 'pie'). In a 2-player PIE session EVERY client has its OWN widgets, so the default may well read the other player's HUD.
num_loopsNoOptional int number of loops (default 1).
play_modeNoOptional Forward | Reverse | PingPong (default Forward).
restore_stateNoOptional bool: restore the pre-animation state on finish (default false).
start_at_timeNoOptional float seconds to start playback at (default 0).
animation_nameYesobject name OR display label of the animation to play
blueprint_nameNoAlias of `widget_bp_path` (same value, same meaning). Accepted because sibling tools spell this parameter differently; prefer `widget_bp_path`.
playback_speedNoOptional float speed multiplier (default 1.0).
widget_bp_pathNo/Game path of the Widget Blueprint asset

Schema Changelog

Changes observed during successful MCP inspections.

  1. First observedv1.1.0

TDQS

A3.9/5.0
Behavior4/5

Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

Annotations cover the safety profile (destructive=true, non-idempotent), so the description's job is to go beyond them — and it does, disclosing the exact fallback payload (played:false, headless:true, requires_pie:true) and the required PIE/live-widget precondition. It stops short of explaining side effects such as save behavior implied by the 'saved' field or the semantics of destructiveHint=true.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Conciseness4/5

Is the description appropriately sized, front-loaded, and free of redundancy?

Front-loaded with the purpose, then a compact behavior note, then a Returns block. The return-field enumeration is long but justified because no output schema exists. Every sentence carries weight.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Completeness4/5

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

With 9 parameters, no output schema, and mutation annotations, the description compensates by disclosing the return shape and the PIE dependency. It is largely complete, missing only notes on save persistence and the reason for the destructive hint.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Parameters3/5

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema description coverage is 100% and the world selector already carries rich semantics (PIE/server/client, 2-player caveat, blueprint_name aliasing), so the schema does the heavy lifting. The description adds no parameter-level detail beyond what the schema provides, which is the baseline 3.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Purpose4/5

Does the description clearly state what the tool does and how it differs from similar tools?

The opening sentence gives a specific verb+resource ('Play a widget animation') and the follow-up distinguishes real UUserWidget::PlayAnimation playback from the headless fallback. It does not, however, explicitly contrast itself with close siblings like play_animation (skeletal/actor) or stop_widget_animation.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Usage Guidelines4/5

Does the description explain when to use this tool, when not to, or what alternatives exist?

The description clearly states the runtime precondition: real playback requires a live PIE instance of the WidgetBP, otherwise it degrades to a documented headless gate. That is a strong 'when it works / when it doesn't' signal, but no alternative tool is named for the non-PIE case.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.

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