browser_setViewport

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

With no annotations, the description must disclose behavioral traits. It only states the action and a use case, but does not explain whether the change applies to the current tab, whether it causes a reload, or how it affects subsequent operations. This is minimal information.

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?

Two short sentences, no filler. The first sentence states the action, the second gives the use case. Very efficient.

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 setter with two parameters and no output schema, the description is adequate but could mention the scope (current tab) and that the change applies to subsequent browser interactions. Given the minimal complexity, a score of 3 is appropriate.

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 schema already provides complete descriptions for both parameters (width and height with units and defaults). The description 'width × height' adds no new meaning, so it meets the baseline of 3.

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 uses a specific verb 'Change' and identifies the resource 'viewport size' with dimensions. It clearly distinguishes from sibling tools like browser_goto or browser_screenshot by focusing on viewport configuration.

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 'Useful for responsive testing' provides a clear context for when to use the tool, though it does not explicitly exclude alternatives. There is no competing viewport tool among siblings, so this guidance is sufficient.

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