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

The description adds significant behavioral context beyond the annotations: it uses headless Chromium, measures with real getBoundingClientRect values, filters elements below the threshold, emits concrete CSS fixes, tells exactly what fields appear, and sorts worst-first. It also clearly distinguishes the browser mode from the pure snapshot mode, which is important for an agent predicting side effects. No contradiction with the annotations was found.

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 dense but highly organized, front-loaded with purpose in the first clause, followed by a clear actor list and a structured output specification. The two-mode sentence elegantly distinguishes use cases without forcing the agent to open the schema or infer behavior.

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 no-output-schema tool, the description fully specifies the return format, the threshold criteria, the element coverage, the sorting, and the two possible invocation modes. The absence of an output schema is compensated for well by this exposition. The only implicit rule is that url and elements should be treated as exclusive modes, but the wording strongly implies this.

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?

Even though schema coverage is 100%, the description materially enriches every parameter: url is tied to browser rendering, elements is tied to the no-render snapshot pathway, and minSize default of 44px is restated and connected to the WCAG/Apple requirement. It explains when each parameter is relevant and how they differ in execution, beyond the literal schema descriptions.

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 plus resource: a WCAG 2.5.5 / Apple 44pt tap-target audit for web pages. It goes further by enumerating which element types are collected and exactly what the per-element output contains, making its scope unambiguous and easily distinguished from sibling audits like audit_contrast or audit_ios_a11y.

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 gives clear operational guidance with two explicit invocation modes: pass a url for real headless chromium measurement, or pass a pre-collected elements snapshot when a browser should not be involved. It also states the 'for the web' context, but it does not explicitly name sibling alternatives for native/mobile audits or state when this tool should not be used.

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