レイアウト破綻の検査

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

Annotations already declare readOnlyHint=true and idempotentHint=true; the description reinforces and extends this by stating no baseline image is needed, that measurement is done via DOM coordinates and text drawing rectangles, and that verdicts are classified as 'static' or 'candidate' to indicate certainty. This adds meaningful behavioral context beyond the annotations.

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 well-structured with clear sections for purpose, detections, arguments, return value, and exclusions. It is information-dense but not bloated; however, it does partially restate parameter details already present in the schema, which keeps it from a perfect score.

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 an 11-parameter tool with no output schema, the description thoroughly covers the return shape (summary plus findings with check/severity/verdict/elements/evidence/suggest) and explains the static/candidate verdict nuance. It also documents exclusions, defaults, and required inputs, making it nearly self-contained.

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 baseline is 3. The description adds value by explaining the one-of constraint for html/path/url, the reason viewport has no default, and the default values for checks and format. It does not explain every parameter in detail, but it meaningfully supplements the schema.

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 tool renders HTML to detect layout breakage and provides a concrete list of detectable issues (text overlap, overflow, horizontal scroll, unexpanded placeholders, broken references, duplicate IDs, invisible text). It also explicitly notes it is inspection-only and does not modify files, distinguishing its purpose.

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?

The description explicitly says when to use it (detect layout breakage) and when not to use it (excludes design evaluation, accessibility contrast checks, and before/after diff comparison). It also clarifies key constraints such as providing exactly one of html/path/url and the viewport being mandatory because width affects results.

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