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by CarlxsMG
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set_niagara_renderer_material

DestructiveIdempotent

Assign a material asset to a Niagara renderer's Material field (Sprite/Ribbon/Mesh), then compile and save the system and read back the material path for verification.

Instructions

Set the Material UPROPERTY on a Niagara renderer (Sprite/Ribbon/Mesh). Loads the material, sets it on the renderer's public Material field, requests a system compile and saves. Reads back to verify the material path is now bound.

Returns: { system_path: string, emitter_name: string, renderer_index: int, renderer_class: string, material_path: string, material_path_read_back: string, save_error?: string }

Input Schema

TableJSON Schema
NameRequiredDescriptionDefault
system_pathYesAsset path of the Niagara System.
emitter_nameYesName of the emitter handle.
material_pathYesAsset path of the UMaterialInterface to assign.
renderer_indexYes0-based index of the renderer (use get_niagara_emitter_renderers to find the index)

Schema Changelog

Changes observed during successful MCP inspections.

  1. Changed1 schema field changedv1.2.0
    • changedInput schema / required
      Previous value: -[
-  "emitter_name",
-  "renderer_index",
-  "material_path"
-]New value: +[
+  "system_path",
+  "emitter_name",
+  "renderer_index",
+  "material_path"
+]
  2. 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, idempotentHint=true, and non-read-only, but the description goes further by disclosing the full side-effect chain: it loads the material, sets it on the public field, triggers a system compile, and saves the asset. It also surfaces a save_error field, which is valuable mutation context. It stops short of stating that the existing material assignment is replaced or what happens on material load failure.

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

Conciseness5/5

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

The action is front-loaded in the first sentence, the side-effect sequence follows, and the return shape is compact. Every sentence earns its place, with no redundancy.

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 no output schema, documenting the return object (including material_path_read_back and optional save_error) is important and done well. Combined with the annotations and full schema coverage, an agent has what it needs to call this correctly; only edge-case behavior (failed load, overwrite semantics) is absent.

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 all four parameters are already documented in the schema (including the hint to use get_niagara_emitter_renderers for renderer_index). The description adds no additional syntax or format meaning beyond the schema, so the baseline of 3 applies.

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 and resource ('Set the Material UPROPERTY on a Niagara renderer') and enumerates the applicable renderer kinds (Sprite/Ribbon/Mesh), which an agent can use to distinguish it from set_niagara_decal_renderer_material and set_niagara_mesh_renderer_mesh among the siblings.

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?

The parenthetical (Sprite/Ribbon/Mesh) implies scope and implicitly excludes decal renderers, but there is no explicit when-to-use/when-not statement or named alternative for other renderer material cases. Usage is inferable rather than stated.

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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