browser_set_viewport

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

Annotations indicate readOnlyHint=false, and description states 'Resize,' confirming it's a mutation. Description adds context about responsive testing and presets, surpassing what annotations alone provide. No contradictions.

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?

Extremely concise: two sentences for purpose and usage, plus a cleanly formatted list of presets. Every sentence is meaningful and well-front-loaded.

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 tool (2 required params, output schema exists), the description covers purpose, when to call, and provides presets. No gaps given the available structured information.

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 covers both parameters (100% coverage), but description adds value with common presets and a use-case framework, making it easier for the agent to choose values. Baseline is 3, so this is above.

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?

Description clearly states 'Resize the browser viewport to test responsive / mobile layouts,' using a specific verb and resource. This distinguishes it from sibling tools like browser_navigate or browser_click.

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?

Explicitly says 'Call this at any point during a session to switch between breakpoints,' providing clear usage context. However, it doesn't specify when not to use or mention alternatives, though the presets list helps.

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