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by CarlxsMG
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bind_widget_to_viewmodel

Destructive

Adds a verified MVVM binding to a Widget Blueprint, connecting a widget property to a viewmodel property using resolved paths.

Instructions

Append an FMVVMBlueprintViewBinding to a Widget BP's MVVM authoring state, with a REAL SourcePath/DestinationPath (resolved via reflection and written through UMVVMEditorSubsystem, then re-read to verify the write actually stuck).

Returns: { widget_blueprint_name, source_path, destination_path, binding_mode, created, binding_count, binding_id, source_path_verified, destination_path_verified, has_mvvm_extension }

Input Schema

TableJSON Schema
NameRequiredDescriptionDefault
forceNoOptional. This command is REFUSED while a Play-in-Editor session is running: it either compiles a Blueprint (the reinstancer can retain a world, and CheckForWorldGCLeaks is Fatal -- it KILLS the editor) or writes to disk (Editor.AllowSavingAssetsDuringPIE=0 makes the engine refuse the write, so it would report success without writing a byte). Stop PIE and retry instead; force=true runs it anyway, at your own risk.
source_pathYes"ViewModel.Property" (exactly one dot): ViewModel = an existing viewmodel context name (added via add_viewmodel), Property = a reflected property on that viewmodel's class. Multi-segment ("A.B.C") is NOT supported.
binding_modeNooptional: "OneWay" (default), "TwoWay", "OneTime", "OneWayToSource"
destination_pathYes"Widget.Property" (exactly one dot): Widget = a widget name in this Widget BP's WidgetTree, Property = a reflected property on that widget's class. Multi-segment is NOT supported.
widget_blueprint_nameYes/Game path of the Widget Blueprint asset

Schema Changelog

Changes observed during successful MCP inspections.

  1. First observedv1.1.0

TDQS

A4/5.0
Behavior4/5

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

Annotations already declare destructiveHint=true and idempotentHint=false, so the write/mutation profile is known. The description goes beyond that: it discloses the write path (reflection + UMVVMEditorSubsystem) and a re-read verification step with per-path verified flags, which is genuinely useful behavioral context. It stops short of stating failure semantics or permission requirements.

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 action and resource, and the returns block is compact and scannable. However, the opening sentence is a long run-on packing mechanism and verification into one clause, which slightly hurts readability.

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

Completeness5/5

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

With no output schema, the description's explicit Returns list (including the verification booleans and binding_count) is essential and present. Combined with 100% param coverage and the annotation safety profile, an agent has enough to call it correctly; only the when-to-use angle is thin.

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 coverage is 100%, so the schema already documents all five parameters, including the detailed force/PIE caveat and the single-dot path format. The description only reinforces that paths are 'REAL' and reflection-resolved, which is marginal added meaning. Baseline 3 applies when the schema does the heavy lifting.

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

Purpose5/5

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

States a specific verb ('Append') and resource ('FMVVMBlueprintViewBinding to a Widget BP's MVVM authoring state'), including the mechanism (reflection, UMVVMEditorSubsystem). An agent can distinguish this from the sibling unbind_widget_from_viewmodel and list_widget_property_bindings without opening any schema.

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

Usage Guidelines3/5

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

Usage is implied by the verb 'append' (add a new binding), but there is no explicit when-to-use, when-not-to-use, or named alternative. It never says to call unbind_widget_from_viewmodel to remove one, nor references add_viewmodel as a prerequisite for the viewmodel context. The PIE restriction is documented, but only in the schema's force param, not the description.

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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