getViewport

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

With no annotations provided, the description carries the full burden of behavioral disclosure. The verb 'Get' implies a read-only operation, and the description specifies the two outputs (size and pixel ratio). However, it does not explicitly state that there are no side effects, nor does it describe the exact return format, which would be valuable for transparency.

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 exceptionally concise: two short sentences that front-load the action and purpose. Every word earns its place, with no filler or redundant content.

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?

Given the low complexity (no parameters, no output schema), the description adequately covers the essentials: what it does and a key use case. It lacks details about return formatting or edge cases, but for a simple getter tool, this is largely sufficient. The absence of an output schema slightly raises the bar, but the description's explicit mention of the returned values helps bridge that gap.

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 tool has zero parameters, so the baseline per rubric is 4. The description adds semantic value by telling the user what information the tool returns (viewport size and pixel ratio), which goes beyond the empty input schema and compensates for the lack of an output 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 tool's function: to get viewport size and pixel ratio. It uses a specific verb ('Get') and resource ('viewport'), and distinguishes it from sibling tools like setViewport, which performs the opposite action. The mention of 'pixel ratio' adds precision about what is retrieved.

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 phrase 'For responsive design testing' provides clear context for when to use this tool. However, it does not explicitly mention alternatives or exclusions, such as contrasting with setViewport for changing the viewport. This is clear but lacks direct comparative guidance.

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