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Eminemminem

BlenderMCP

by Eminemminem

get_polyhaven_categories

Retrieve category lists for Polyhaven assets to organize and filter 3D resources in Blender. Specify asset type (HDRI, textures, models) to access structured browsing options.

Instructions

Get a list of categories for a specific asset type on Polyhaven.

Parameters:

  • asset_type: The type of asset to get categories for (hdris, textures, models, all)

Input Schema

TableJSON Schema
NameRequiredDescriptionDefault
asset_typeNohdris

Implementation Reference

  • The core handler implementation for the get_polyhaven_categories MCP tool. It proxies the request to the Blender addon via socket command, handles PolyHaven enabled check, formats and sorts the categories response for user readability.
    @mcp.tool()
    def get_polyhaven_categories(ctx: Context, asset_type: str = "hdris") -> str:
        """
        Get a list of categories for a specific asset type on Polyhaven.
        
        Parameters:
        - asset_type: The type of asset to get categories for (hdris, textures, models, all)
        """
        try:
            blender = get_blender_connection()
            if not _polyhaven_enabled:
                return "PolyHaven integration is disabled. Select it in the sidebar in BlenderMCP, then run it again."
            result = blender.send_command("get_polyhaven_categories", {"asset_type": asset_type})
            
            if "error" in result:
                return f"Error: {result['error']}"
            
            # Format the categories in a more readable way
            categories = result["categories"]
            formatted_output = f"Categories for {asset_type}:\n\n"
            
            # Sort categories by count (descending)
            sorted_categories = sorted(categories.items(), key=lambda x: x[1], reverse=True)
            
            for category, count in sorted_categories:
                formatted_output += f"- {category}: {count} assets\n"
            
            return formatted_output
        except Exception as e:
            logger.error(f"Error getting Polyhaven categories: {str(e)}")
            return f"Error getting Polyhaven categories: {str(e)}"
  • Input schema documentation for the tool, specifying the asset_type parameter and its possible values.
    """
    Get a list of categories for a specific asset type on Polyhaven.
    
    Parameters:
    - asset_type: The type of asset to get categories for (hdris, textures, models, all)
    """
  • MCP tool registration decorator that registers the get_polyhaven_categories function as an MCP tool.
    @mcp.tool()
Behavior2/5

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

No annotations are provided, so the description carries the full burden of behavioral disclosure. It only states the basic action ('Get a list') without detailing response format, error handling, rate limits, authentication needs, or whether it's read-only or has side effects. For a tool with no annotation coverage, this leaves significant gaps in understanding its behavior.

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 concise and well-structured: a clear purpose statement followed by a parameter explanation. It avoids redundancy and wastes no words, though it could be slightly more front-loaded by integrating the parameter details into the initial sentence for better flow.

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

Completeness2/5

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

Given the lack of annotations and output schema, the description is incomplete. It covers the basic purpose and parameter semantics but omits critical details like return format, error conditions, and behavioral traits. For a tool with no structured data support, this leaves the agent inadequately informed about how to handle responses or potential issues.

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

Parameters4/5

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

The description adds meaningful context beyond the input schema: it explains that the asset_type parameter accepts specific values ('hdris, textures, models, all'), which the schema does not specify (schema description coverage is 0%). This compensates for the lack of schema documentation, though it doesn't detail default behavior or constraints beyond the enumerated list.

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 the tool's purpose: 'Get a list of categories for a specific asset type on Polyhaven.' It specifies the verb ('Get'), resource ('categories'), and domain ('Polyhaven'), making the intent unambiguous. However, it does not explicitly differentiate from sibling tools like 'search_polyhaven_assets' or 'get_polyhaven_status', which could provide similar or overlapping functionality.

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?

The description provides minimal guidance: it mentions the asset_type parameter but offers no context on when to use this tool versus alternatives. There is no mention of prerequisites, typical use cases, or comparisons to sibling tools like 'search_polyhaven_assets', leaving the agent with little direction on optimal usage scenarios.

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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