set_device_metrics

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

No annotations are provided, so the description carries the full behavioral burden, and it discloses almost nothing: it does not say whether the emulation applies immediately, whether it persists for the session, how it interacts with previously set metrics, or that width/height are mandatory. "Emulate" implies a transient, non-destructive override but that is left to inference.

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?

A single front-loaded sentence with zero filler; the core resource is stated first and the parenthetical efficiently lists the covered properties.

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 5-parameter tool with no annotations, no output schema, and 0% schema coverage, the description is too thin. It leaves the session scope, default handling, and the distinction from set_viewport_size entirely unaddressed, which an agent needs before invoking 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?

Schema description coverage is 0%, so the description must compensate. It does map its concepts onto the parameters it names (viewport size→width/height, device scale factor→deviceScaleFactor, mobile→mobile), which is genuine added meaning, but it omits units, the meaning of scale factor values, and the defaults declared in the schema (mobile=false, deviceScaleFactor=1), and says nothing about sessionId.

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 gives a specific verb ("Emulate") and resource ("device metrics") and enumerates the components it governs (viewport size, device scale factor, mobile). However, it never distinguishes itself from the sibling set_viewport_size, whose name suggests overlapping viewport control, so an agent cannot tell the two apart from the text alone.

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?

There is no when-to-use guidance, no prerequisites, and no mention of the obvious alternative set_viewport_size or how it relates. The agent must infer all routing decisions from the tool name.

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