BlenderMCP

Instructions

Implementation Reference

• src/blender_mcp/server.py:521-537 (handler)

  The primary handler for the 'get_polyhaven_status' tool. Decorated with @mcp.tool() for registration. Sends a command to the Blender connection to retrieve PolyHaven status and formats the response.

  @mcp.tool()
  def get_polyhaven_status(ctx: Context) -> str:
      """
      Check if PolyHaven integration is enabled in Blender.
      Returns a message indicating whether PolyHaven features are available.
      """
      try:
          blender = get_blender_connection()
          result = blender.send_command("get_polyhaven_status")
          enabled = result.get("enabled", False)
          message = result.get("message", "")
          if enabled:
              message += "PolyHaven is good at Textures, and has a wider variety of textures than Sketchfab."
          return message
      except Exception as e:
          logger.error(f"Error checking PolyHaven status: {str(e)}")
          return f"Error checking PolyHaven status: {str(e)}"

• src/blender_mcp/server.py:521-521 (registration)

  The @mcp.tool() decorator registers the get_polyhaven_status function as an MCP tool.

  @mcp.tool()

• src/blender_mcp/server.py:206-236 (helper)

  Helper function get_blender_connection() that uses get_polyhaven_status to validate connection and cache PolyHaven enabled status.

  def get_blender_connection():
      """Get or create a persistent Blender connection"""
      global _blender_connection, _polyhaven_enabled  # Add _polyhaven_enabled to globals
      
      # If we have an existing connection, check if it's still valid
      if _blender_connection is not None:
          try:
              # First check if PolyHaven is enabled by sending a ping command
              result = _blender_connection.send_command("get_polyhaven_status")
              # Store the PolyHaven status globally
              _polyhaven_enabled = result.get("enabled", False)
              return _blender_connection
          except Exception as e:
              # Connection is dead, close it and create a new one
              logger.warning(f"Existing connection is no longer valid: {str(e)}")
              try:
                  _blender_connection.disconnect()
              except:
                  pass
              _blender_connection = None
      
      # Create a new connection if needed
      if _blender_connection is None:
          _blender_connection = BlenderConnection(host="localhost", port=9876)
          if not _blender_connection.connect():
              logger.error("Failed to connect to Blender")
              _blender_connection = None
              raise Exception("Could not connect to Blender. Make sure the Blender addon is running.")
          logger.info("Created new persistent connection to Blender")
      
      return _blender_connection

• src/blender_mcp/server.py:874-938 (helper)

  The asset_creation_strategy prompt recommends using get_polyhaven_status() to check PolyHaven availability before asset creation.

  @mcp.prompt()
  def asset_creation_strategy() -> str:
      """Defines the preferred strategy for creating assets in Blender"""
      return """When creating 3D content in Blender, always start by checking if integrations are available:
  
      0. Before anything, always check the scene from get_scene_info()
      1. First use the following tools to verify if the following integrations are enabled:
          1. PolyHaven
              Use get_polyhaven_status() to verify its status
              If PolyHaven is enabled:
              - For objects/models: Use download_polyhaven_asset() with asset_type="models"
              - For materials/textures: Use download_polyhaven_asset() with asset_type="textures"
              - For environment lighting: Use download_polyhaven_asset() with asset_type="hdris"
          2. Sketchfab
              Sketchfab is good at Realistic models, and has a wider variety of models than PolyHaven.
              Use get_sketchfab_status() to verify its status
              If Sketchfab is enabled:
              - For objects/models: First search using search_sketchfab_models() with your query
              - Then download specific models using download_sketchfab_model() with the UID
              - Note that only downloadable models can be accessed, and API key must be properly configured
              - Sketchfab has a wider variety of models than PolyHaven, especially for specific subjects
          3. Hyper3D(Rodin)
              Hyper3D Rodin is good at generating 3D models for single item.
              So don't try to:
              1. Generate the whole scene with one shot
              2. Generate ground using Hyper3D
              3. Generate parts of the items separately and put them together afterwards
  
              Use get_hyper3d_status() to verify its status
              If Hyper3D is enabled:
              - For objects/models, do the following steps:
                  1. Create the model generation task
                      - Use generate_hyper3d_model_via_images() if image(s) is/are given
                      - Use generate_hyper3d_model_via_text() if generating 3D asset using text prompt
                      If key type is free_trial and insufficient balance error returned, tell the user that the free trial key can only generated limited models everyday, they can choose to:
                      - Wait for another day and try again
                      - Go to hyper3d.ai to find out how to get their own API key
                      - Go to fal.ai to get their own private API key
                  2. Poll the status
                      - Use poll_rodin_job_status() to check if the generation task has completed or failed
                  3. Import the asset
                      - Use import_generated_asset() to import the generated GLB model the asset
                  4. After importing the asset, ALWAYS check the world_bounding_box of the imported mesh, and adjust the mesh's location and size
                      Adjust the imported mesh's location, scale, rotation, so that the mesh is on the right spot.
  
                  You can reuse assets previous generated by running python code to duplicate the object, without creating another generation task.
  
      3. Always check the world_bounding_box for each item so that:
          - Ensure that all objects that should not be clipping are not clipping.
          - Items have right spatial relationship.
      
      4. Recommended asset source priority:
          - For specific existing objects: First try Sketchfab, then PolyHaven
          - For generic objects/furniture: First try PolyHaven, then Sketchfab
          - For custom or unique items not available in libraries: Use Hyper3D Rodin
          - For environment lighting: Use PolyHaven HDRIs
          - For materials/textures: Use PolyHaven textures
  
      Only fall back to scripting when:
      - PolyHaven, Sketchfab, and Hyper3D are all disabled
      - A simple primitive is explicitly requested
      - No suitable asset exists in any of the libraries
      - Hyper3D Rodin failed to generate the desired asset
      - The task specifically requires a basic material/color
      """