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Unreal-MCP

Unreal-MCP

by aadeshrao123
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set_mesh_material_color

Modify a mesh component's material color by providing RGBA values (0-1) and optional material path, slot, and parameter name.

Instructions

Set material color on a mesh component.

color: [R, G, B, A] values 0-1

Tool call template

Replace each placeholder with a value matching the input schema. Only required parameters are included; add optional parameters as needed.

{
  "id": 1,
  "jsonrpc": "2.0",
  "method": "tools/call",
  "params": {
    "arguments": {
      "blueprint_name": "<blueprint_name>",
      "component_name": "<component_name>",
      "color": "<color>"
    },
    "name": "set_mesh_material_color"
  }
}

Input Schema

NameRequiredDescriptionDefault
colorYes
material_pathNo/Engine/BasicShapes/BasicShapeMaterial
material_slotNo
blueprint_nameYes
component_nameYes
parameter_nameNoBaseColor

Output Schema

NameRequiredDescriptionDefault
resultYes

Schema Changelog

Changes observed during successful MCP inspections.

  1. First observedv1.2.1

TDQS

C2.4/5.0
Behavior2/5

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

No annotations are provided, so the description must disclose behavioral traits. It does not mention side effects, whether it modifies a material instance or creates a new one, or whether it applies in the editor or runtime. The description only states 'set material color.'

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

Conciseness3/5

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

The description is short and front-loads the purpose, with a separate line for the color format. However, it is too terse given the six parameters; it omits essential details that would make it more useful.

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

Completeness1/5

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

Given the tool has 6 parameters (3 required) and no schema description coverage, the description is severely incomplete. It does not explain the required parameters blueprint_name and component_name, the optional material_path, material_slot, or parameter_name. The presence of an output schema does not excuse the lack of explanation of inputs.

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

Parameters1/5

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

Schema description coverage is 0%. The description only explains the 'color' parameter format (array of 0-1 values). The other 5 parameters (blueprint_name, component_name, material_path, material_slot, parameter_name) are not explained at all, leaving the agent to infer their meaning from names alone, which is insufficient.

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 description clearly states it sets material color on a mesh component, including the color format. It's a specific verb and resource, but does not explicitly differentiate from sibling tools like apply_material_to_actor or set_material_instance_parameter.

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

Usage Guidelines2/5

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

No guidance on when to use this tool versus alternatives, no prerequisites (e.g., mesh must have material), and no mention of when to prefer other material-related tools.

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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