perch_set_viewport

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

With no annotations, the description carries the full burden. It usefully discloses the dual nature of the operation (mutates the live preview AND returns the iframe rect), but says nothing about permissions, whether resizing persists, or how it interacts with other preview state.

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 compact sentence, front-loaded with the primary verb and effect, with no filler or redundancy.

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 two-param tool with defaults, the essentials are present, but there is no output schema and the description does not specify the shape of the reported rect or the units of width/height. 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 coverage is 100%, but the schema descriptions only give defaults ('Default 1500'/'Default 950') without units, and the tool description adds no meaning beyond echoing that a rect is produced. Baseline 3 for full schema coverage with no extra semantic value in the description.

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 ('Resize') and resource ('the live preview'), plus a secondary effect ('report the iframe rect'). An agent can tell what it does, though the description does not relate it to any sibling (e.g. perch_shot/perch_navigate) even though none of them resize.

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 condition, no prerequisites, and no mention of alternatives. The agent must infer that this is a setup step before capturing or inspecting a preview; the description gives none of that context explicitly.

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