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clear_mpci_parameter_overrides

DestructiveIdempotent

Resets a Material Parameter Collection Instance on a world to its default scalar and vector values by clearing all overrides. Use for runtime-only rollback of per-world MPC changes; nothing is saved.

Instructions

Reset the Material Parameter Collection Instance (MPCI: the transient per-world values of a collection asset) of one collection on a world, the editor world by default, to the collection's default values by dropping all its scalar and vector overrides. Runtime only: nothing is saved, no undo. The engine creates the instance on lookup when the world has none, so a missing instance is not an error. scalars_reset_to_default and vectors_reset_to_default count parameters now reading their default. For a Material Instance Constant asset use clear_material_parameter_overrides.

Returns: { collection_path: string, world_name: string, scalar_count: int, vector_count: int, scalars_reset_to_default: int, vectors_reset_to_default: int, cleared: bool }

Input Schema

TableJSON Schema
NameRequiredDescriptionDefault
world_labelNoEmpty or "editor" for the editor world (the default); otherwise the UWorld name of a live world context, compared case-insensitively (first match)
collection_pathYesFull /Game path of the parent MPC

Schema Changelog

Changes observed during successful MCP inspections.

  1. Changed1 schema field changedv1.2.0
    • changedInput schema / properties / world_label / description
      Previous value: -"Optional world context label, default editor"New value: +"Empty or \"editor\" for the editor world (the default); otherwise the UWorld name of a live world context, compared case-insensitively (first match)"
  2. First observedv1.1.0

TDQS

A4.4/5.0
Behavior5/5

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

Beyond the annotations, it discloses runtime-only semantics, that nothing is saved and there is no undo, and the important edge case that a missing instance is auto-created on lookup and therefore not an error. It also explains what the reset-count return fields mean. This is behavior context the annotations do not carry.

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?

The description is front-loaded with the purpose, then the runtime caveat, edge case, sibling pointer, and return shape in a logical order. It is dense but every sentence contributes; it is slightly longer than strictly necessary but nothing is wasted.

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?

For a mutating tool with annotations covering destructive/idempotent flags and no output schema, the description covers persistence, undo, the auto-create edge case, and even enumerates the return fields. Nothing an agent needs to call it correctly is missing.

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%, so the schema already documents collection_path and world_label including the editor-world default. The description adds no syntax or format detail beyond the schema, making the baseline 3 appropriate.

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?

The description names a precise verb (reset/clear) and resource (MPCI of one collection on a world), defines the abbreviation inline, and explicitly distinguishes itself from the sibling clear_material_parameter_overrides. An agent can tell exactly what operation this performs and on what object.

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?

It names the alternative tool (clear_material_parameter_overrides) and the condition that selects it (Material Instance Constant asset), and states the default world (editor world). It lacks an explicit 'when not to use' beyond the sibling pointer, so it falls short of the full 5.

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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