Check Mobile

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

With readOnlyHint=true, the safety profile is already known. The description adds meaningful behavior: headless browser execution, exact viewport (375x812), mobile User-Agent, and the specific checks performed. It also discloses the return of a mobile screenshot, going beyond the annotation.

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 two sentences, front-loading the core purpose and context. Every detail (viewport size, user-agent, check categories, screenshot output) earns its place without redundancy or filler.

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?

The tool is simple (one parameter, no output schema), and the description captures the inputs, execution context, checks, and output. It does not explicitly state what form the audit findings take beyond the screenshot, but the provided detail is sufficient for correct invocation.

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?

The schema covers 100% of parameters—only 'url'—with a clear description. The tool description does not add parameter-specific semantics, but none are needed since the schema is complete and the parameter is self-explanatory. Baseline 3 is appropriate.

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 uses a specific verb ('Audit') with a clear resource ('a web page for mobile-friendliness') and lists concrete checks (viewport meta, horizontal scroll, font sizes, tap target sizes). This clearly distinguishes it from siblings like screenshot, check_performance, and check_accessibility.

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 establishes a clear context for use: when a mobile-friendliness audit is needed, using a specific iPhone viewport and mobile user-agent. It does not explicitly name sibling tools or state when not to use it, but the context is unambiguous enough for an agent to select it appropriately.

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