set_viewport_size

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

Although annotations indicate this is a write operation (readOnlyHint: false), the description adds no additional behavioral context. It does not disclose whether the change affects subsequent screenshots, navigation, or other operations, nor does it mention any limitations or side effects. With annotations present, the description could have provided more value but falls short.

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 extremely concise at one sentence (4 words). It contains no unnecessary words and gets straight to the point. However, it is so brief that it sacrifices some helpful context, preventing a perfect score.

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 tool's simplicity (two parameters, no output schema), the description is minimally adequate. However, it lacks context about what 'viewport' refers to (e.g., current page or global setting) and does not mention any dependencies or effects. While it satisfies the basic need, it is not fully complete for an agent to use confidently.

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 input schema has 100% coverage with descriptions for each parameter ('Width in pixels', 'Height in pixels'). The description adds no extra meaning beyond the schema, so a baseline score of 3 is appropriate. No constraints or additional semantics are provided.

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 action (set) and the resource (viewport dimensions) with units (in pixels). It is specific and distinct from sibling tools like screenshot or navigation functions, which don't involve resizing.

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?

No guidance is provided on when to use this tool versus alternatives. There is no mention of prerequisites, side effects, or context such as whether it applies to the current page or all pages. The agent is left to infer usage from the name alone.

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