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

With no annotations provided, the description carries the full burden of behavior disclosure. It clearly states that this only changes the window, is not a device emulator, and that a real handset is the only honest test. It also explains the fixed-screen rationale, which adds context beyond the schema. However, it doesn't mention return values or side effects, though these may be minimal for a resize operation. The disclosure is strong but not exhaustive.

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 two dense sentences with no fluff. It front-loads the action and then provides necessary caveats and alternatives. Every sentence earns its place, and it avoids redundancy with the schema.

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 with three well-documented parameters and no output schema, the description covers the purpose, usage constraints, limitations, and an explicit alternative. It explains why it's not a device and how to get a real device instead. Nothing essential is missing for an agent to decide when and how to use it correctly.

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 schema has 100% coverage with descriptions for all three parameters: width, height, and pageId. The description only reiterates 'by pageId' without adding additional meaning, such as units or source. Since the schema already documents each parameter adequately, the description adds minimal value here, consistent with a baseline score of 3.

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 verb 'Resize', the resource 'DESKTOP grid browser viewport', and the method 'by pageId'. It also explicitly contrasts with a real device, making it distinct from sibling tools like device_rotate or ios_window_size. The purpose is unambiguous and specific.

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 states when to use: 'for checking responsive breakpoints without a real handset' and when not to use: 'A real phone is still the honest test; this only changes the window.' It also provides an explicit alternative: 'pick a different device by udid instead' and explains why there is no webpage_resize. This gives clear routing and exclusions.

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