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

Annotations already disclose readOnlyHint=false, destructiveHint=false, idempotentHint=false, and openWorldHint=true. The description adds valuable behavioral context beyond annotations: it only changes the window, does not emulate a device, and clarifies there is no webpage_resize. It does not contradict annotations and adds meaningful usage semantics.

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 core action is front-loaded in the first clause. The remaining sentences are mostly justified by disambiguation, though the em-dash phrasing and repeated caveats make it slightly longer than strictly necessary. It is well-structured but not maximally tight.

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 viewport-mutation tool with no output schema and full annotation coverage, the description is largely complete: it explains the action, its scope, and its relationship to device emulation. It does not explain whether the resize persists across navigations or affects screenshots, which would be minor helpful additions.

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 100%, so all three parameters are already documented with descriptions (width, height, pageId). The description only references 'pageId' and implies width/height via 'viewport', adding no syntax or format details beyond the schema. Baseline 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 states a specific verb and resource: 'Resize the DESKTOP grid browser viewport (by pageId)'. It explicitly distinguishes this from device resizing by saying it is NOT a device and that there is no webpage_resize, so an agent can differentiate it from sibling tools without inspecting schemas.

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 a clear purpose context ('for checking responsive breakpoints without a real handset'), an explicit exclusion ('NOT a device'), and a concrete alternative ('pick a different device by udid instead'). This covers when to use, when not to use, and what to use instead.

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