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get_viewport_screenshot

Capture screenshots of the Blender 3D viewport for documentation, sharing, or progress tracking. Specify maximum image dimensions to control file size.

Instructions

Capture a screenshot of the current Blender 3D viewport.

Parameters:

  • max_size: Maximum size in pixels for the largest dimension (default: 800)

Returns the screenshot as an Image.

Input Schema

TableJSON Schema
NameRequiredDescriptionDefault
max_sizeNo

Implementation Reference

  • The handler function for the 'get_viewport_screenshot' tool. It connects to Blender, sends a command to capture the viewport screenshot to a temp file, reads the image bytes, and returns an MCP Image object. Registered via @mcp.tool() decorator.
    @telemetry_tool("get_viewport_screenshot")
    @mcp.tool()
    def get_viewport_screenshot(ctx: Context, max_size: int = 800) -> Image:
        """
        Capture a screenshot of the current Blender 3D viewport.
        
        Parameters:
        - max_size: Maximum size in pixels for the largest dimension (default: 800)
        
        Returns the screenshot as an Image.
        """
        try:
            blender = get_blender_connection()
            
            # Create temp file path
            temp_dir = tempfile.gettempdir()
            temp_path = os.path.join(temp_dir, f"blender_screenshot_{os.getpid()}.png")
            
            result = blender.send_command("get_viewport_screenshot", {
                "max_size": max_size,
                "filepath": temp_path,
                "format": "png"
            })
            
            if "error" in result:
                raise Exception(result["error"])
            
            if not os.path.exists(temp_path):
                raise Exception("Screenshot file was not created")
            
            # Read the file
            with open(temp_path, 'rb') as f:
                image_bytes = f.read()
            
            # Delete the temp file
            os.remove(temp_path)
            
            return Image(data=image_bytes, format="png")
            
        except Exception as e:
            logger.error(f"Error capturing screenshot: {str(e)}")
            raise Exception(f"Screenshot failed: {str(e)}")
  • The @mcp.tool() decorator registers the get_viewport_screenshot function as an MCP tool, with telemetry tracking.
    @telemetry_tool("get_viewport_screenshot")
    @mcp.tool()
Behavior2/5

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

With no annotations provided, the description carries full burden for behavioral disclosure. It mentions what the tool does but doesn't describe important behavioral aspects: whether it requires specific Blender state, what happens if viewport is empty, performance characteristics, or error conditions. The description is functional but lacks behavioral context.

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 perfectly front-loaded with the core purpose in the first sentence, followed by clear parameter documentation. Every sentence earns its place with no wasted words, and the structure (purpose → parameters → return) is logical and efficient.

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

Completeness3/5

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

For a single-parameter tool with no annotations and no output schema, the description covers the basic functionality adequately but lacks completeness. It doesn't explain the return format ('Image' is vague), doesn't mention what happens if the viewport isn't available, and provides minimal behavioral context. It meets minimum viability but has clear gaps.

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?

With 0% schema description coverage and only one parameter, the description adds significant value by explaining the parameter's purpose ('Maximum size in pixels for the largest dimension') and providing the default value (800). This compensates well for the lack of schema documentation, though it doesn't specify constraints like minimum/maximum values.

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 clearly states the specific action ('Capture a screenshot') and target resource ('current Blender 3D viewport'), distinguishing it from all sibling tools which involve downloading assets, generating models, getting statuses, or importing assets rather than capturing visual output from the viewport.

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 no guidance on when to use this tool versus alternatives, prerequisites, or context. It doesn't mention if this should be used instead of other screenshot methods or in what workflow scenarios it's appropriate, leaving the agent with no usage context.

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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