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Eminemminem

BlenderMCP

by Eminemminem

set_texture

Apply downloaded Polyhaven textures to 3D objects in Blender to enhance visual appearance and material properties.

Instructions

Apply a previously downloaded Polyhaven texture to an object.

Parameters:

  • object_name: Name of the object to apply the texture to

  • texture_id: ID of the Polyhaven texture to apply (must be downloaded first)

Returns a message indicating success or failure.

Input Schema

TableJSON Schema
NameRequiredDescriptionDefault
object_nameYes
texture_idYes

Implementation Reference

  • MCP tool handler for 'set_texture'. Applies a Polyhaven texture to a Blender object by sending a command to the Blender addon. Includes input validation via type hints and docstring, error handling, and detailed response formatting.
    @mcp.tool()
    def set_texture(
        ctx: Context,
        object_name: str,
        texture_id: str
    ) -> str:
        """
        Apply a previously downloaded Polyhaven texture to an object.
        
        Parameters:
        - object_name: Name of the object to apply the texture to
        - texture_id: ID of the Polyhaven texture to apply (must be downloaded first)
        
        Returns a message indicating success or failure.
        """
        try:
            # Get the global connection
            blender = get_blender_connection()
            result = blender.send_command("set_texture", {
                "object_name": object_name,
                "texture_id": texture_id
            })
            
            if "error" in result:
                return f"Error: {result['error']}"
            
            if result.get("success"):
                material_name = result.get("material", "")
                maps = ", ".join(result.get("maps", []))
                
                # Add detailed material info
                material_info = result.get("material_info", {})
                node_count = material_info.get("node_count", 0)
                has_nodes = material_info.get("has_nodes", False)
                texture_nodes = material_info.get("texture_nodes", [])
                
                output = f"Successfully applied texture '{texture_id}' to {object_name}.\n"
                output += f"Using material '{material_name}' with maps: {maps}.\n\n"
                output += f"Material has nodes: {has_nodes}\n"
                output += f"Total node count: {node_count}\n\n"
                
                if texture_nodes:
                    output += "Texture nodes:\n"
                    for node in texture_nodes:
                        output += f"- {node['name']} using image: {node['image']}\n"
                        if node['connections']:
                            output += "  Connections:\n"
                            for conn in node['connections']:
                                output += f"    {conn}\n"
                else:
                    output += "No texture nodes found in the material.\n"
                
                return output
            else:
                return f"Failed to apply texture: {result.get('message', 'Unknown error')}"
        except Exception as e:
            logger.error(f"Error applying texture: {str(e)}")
            return f"Error applying texture: {str(e)}"

Schema Changelog

Changes observed during successful MCP inspections.

  1. First observed

TDQS

A4.3/5.0
Behavior3/5

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

With no annotations, the description must carry the behavioral burden. It discloses the prerequisite of a prior download and states that the tool returns a success/failure message. However, it does not explain what happens on failure, whether existing textures are replaced, or whether the object must exist, leaving moderate behavioral gaps.

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 description is compact, front-loaded with the main purpose, and structured cleanly into purpose, parameters, and return behavior. There is no filler or redundant content beyond what is needed given the 0% schema coverage.

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?

For a simple two-string-parameter tool, the description covers the essential inputs, the prerequisite, and the return behavior. It could be slightly more complete by noting that the object must exist or that the operation may overwrite the object's current texture, but the core invocation context is present.

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

Parameters5/5

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

Schema description coverage is 0%, so the description must fully define the parameters. It does exactly that: object_name is the target object and texture_id is the already-downloaded Polyhaven texture ID. This adds the necessary meaning that the bare schema property names omit.

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 starts with a specific verb-plus-resource statement: 'Apply a previously downloaded Polyhaven texture to an object.' The 'previously downloaded' qualifier clearly distinguishes this from the sibling download_polyhaven_asset and makes the scope of the tool immediately clear.

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 gives a clear usage condition: the texture 'must be downloaded first.' This implies the correct sequence with download_polyhaven_asset, but it does not explicitly name that sibling or state when not to use this tool, so it falls just short of full alternative routing guidance.

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