Screenshot / Editor Viewport

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

Annotations already declare readOnly, idempotent and non-destructive, so the description is free to add genuinely new behavior: the PNG return format, the longest-edge downscaling with aspect preserved, and the headless/--headless failure mode surfacing as a structured error instead of a blank PNG. That last point is exactly the kind of non-obvious operational constraint annotations cannot express.

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?

Three tight sentences: purpose first, then mode selection, then output scaling and the headless caveat. Every sentence contributes distinct information with no repetition of the title or name.

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 single-optional-param read tool with no output schema, the description still covers what is returned (PNG), how it is sized, and how failure manifests. Nothing an agent needs in order to call it correctly and interpret the result is missing.

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?

Schema coverage is 100%, so the mode enum, default and case-insensitivity are already documented in the schema. The description restates them faithfully but adds no syntax or edge-case detail beyond it; baseline 3 is appropriate when the schema carries the parameter burden.

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?

States a specific verb ('Capture') and resource ('Godot editor's main viewport'), and clarifies it is the 3D or 2D editing surface as opposed to the camera or isolated views implied by the sibling tools. An agent can distinguish this from screenshot-camera and screenshot-isolated without opening any schema.

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?

Gives clear selection guidance between '3d' (default) and '2d', and states the precondition that the editor must have a live GPU render. It does not explicitly route the agent to the sibling screenshot tools when the camera or an isolated view is wanted, which is the one remaining gap.

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