browser_set_viewport

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

With no annotations, the description carries the full behavioral burden. It says 'Set' but never states that this mutates persistent browser/session state, whether the viewport resets on navigation or new tabs, or whether it requires an active tab context. That is a notable gap for a state-mutating tool.

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 short sentence with no wasted words, front-loading the primary action. It is efficient, though its brevity also reflects the missing guidance rather than disciplined trimming.

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 4-parameter mutation tool with no annotations and no output schema, the description is minimally viable: it names the action and the two concepts covered by the params. It leaves out prerequisites, tab/session scoping, and sibling disambiguation, so it is adequate but with clear gaps.

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 four parameters (width, height, mobile, device_scale_factor) are already documented with types and defaults. The description adds only the loose phrase 'mobile device emulation', which maps to the mobile and device_scale_factor parameters but adds little beyond the schema. Baseline 3 applies.

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?

States a specific verb (Set) and resource (browser viewport dimensions and mobile device emulation), so the agent knows the core action. However, it does not differentiate itself from overlapping siblings such as browser_set_page_zoom or browser_emulate_environment, so it stops short of a 5.

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 when-to-use guidance, no prerequisites, and no alternatives named. The agent is not told whether this must be called per-tab, before navigation, or how it relates to browser_set_page_zoom / browser_emulate_environment.

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