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

Annotations already declare readOnlyHint=true, idempotentHint=true, destructiveHint=false and openWorldHint=false, so the safety and repeatability profile is covered. The description adds useful motivation for the operation but does not disclose traits beyond annotations, such as whether the viewport change persists across navigations or applies to the session's active tab.

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 tight sentences with the core action front-loaded and the rationale immediately after. Every clause earns its place and there is no filler.

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 no-output-schema tool, the description adequately explains what it does and why, so return values need not be covered. The gap is parameter-level: three of four inputs are undocumented in both schema and description, which leaves an agent guessing at expected values.

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 description coverage is only 25% (only in_workspace is documented). The description mentions no parameters at all, leaving page_id, width and height without units or format guidance (e.g., CSS pixels, which tab is targeted). With low coverage the description should compensate, and it does not.

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 states a specific verb and resource ('Resize the page viewport'), which is unambiguous about the operation. It does not explicitly contrast itself with sibling browser tools such as browser_open or browser_take_screenshot, but the action is distinct enough to be identified without opening the schema.

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?

It gives concrete conditions for use: sites that serve different HTML by viewport width and anti-bot risk scoring by viewport dimensions. That is genuine when-to-use guidance, though it names no alternative tool or exclusion, so it falls short of the 5 level.

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