rhino_viewport_image

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

The description discloses a meaningful behavioral trait beyond the annotations: no render engine is invoked, just a viewport bitmap dump. This helps the agent predict cost and side effects. It also notes that width/height of 0 inherit the on-screen viewport size. It does not discuss file overwrite behavior, but 'save to a PNG file' is sufficient for this simple operation.

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

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

The description is compact and front-loaded with the core purpose. The second sentence adds a justification and a parameter hint without wasted words. Every sentence earns its place, and the structure is easy for an agent to parse quickly.

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

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

For a simple viewport capture tool, the description plus schema provides enough to select and invoke it correctly. It covers the action, the lightweight mechanism, and the key width/height behavior. The output schema handles return-value expectations, so not explaining the return shape is acceptable. The main gap is sparse explanation of the remaining parameters in the description itself.

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

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

The description adds valuable meaning for width and height ('Use 0 to inherit the on-screen viewport size'), which is not obvious from the schema alone. However, schema description coverage is reported as 0%, and the description does not compensate for the remaining parameters such as transparent_bg, view_name, doc_id, or output_path, even though some of those do have descriptions inside the nested schema.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Does the description clearly state what the tool does and how it differs from similar tools?

The description clearly states the action ('Save the current viewport pixels to a PNG file') with a specific verb and resource. It also distinguishes itself from rhino_render_to_file by noting it is a lightweight viewport bitmap dump rather than a rendered output. However, it does not explicitly differentiate from very similar sibling capture tools like rhino_view_capture_to_file or rhino_screenshot, so it stops short of full sibling separation.

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

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

The description gives a clear usage context: use this tool when you need a fast viewport capture without invoking a render engine, and it explicitly names rhino_render_to_file as the heavier alternative. It could be stronger by mentioning when one of the other capture siblings would be more appropriate, but the main decision boundary is clear.

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