set_viewport_size

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

Annotations indicate readOnlyHint=false, so it's a mutation. The description 'Set viewport dimensions' aligns with that, but adds no extra behavioral context like whether it triggers resize events, affects existing pages, or requires an open page. For a mutation tool with no annotations beyond readOnlyHint, more detail is needed.

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 a single efficient sentence with no wasted words. It is appropriately front-loaded and concise.

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?

No output schema and low complexity, but the description omits key context: the effect on the browser window, whether a page must be open, and that subsequent operations (e.g., screenshots) will use the new size. This makes it incomplete for an agent to fully understand the tool's impact.

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% with descriptions 'Width in pixels' and 'Height in pixels'. The tool description adds no further meaning beyond the schema, so baseline score of 3 is appropriate.

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 'Set viewport dimensions in pixels' with a specific verb and resource. The tool is distinct from siblings like screenshot_page or navigate_page, which do not set viewport size. However, it could be slightly more specific about affecting the browser window.

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 provides no guidance on when to use this tool versus alternatives, such as when to resize the viewport before taking screenshots or navigating. No prerequisites or exclusions are mentioned.

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