Check Performance

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

Annotations already indicate readOnlyHint=true, and the description adds meaningful behavioral context: it uses a headless browser, applies network throttling on mobile, and returns a score, timings, network stats, and actionable issues. This goes beyond the annotation without contradicting it.

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?

Two sentences with no wasted words: the first names the metrics and method, the second states profiles and return value. Information is front-loaded and highly scannable.

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 tool with no output schema, the description adequately enumerates the return categories (0-100 score, detailed timings, network stats, actionable issues) and the supported device profiles. Slight gaps remain around the exact shape of the output and any execution-time or cost implications, but the essentials are present.

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 for parameters is 100%, so the schema already documents url and device with descriptions including dimensions and throttling. The description mostly restates the device behavior already in the schema, adding no new parameter-specific meaning.

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 ('Measure') with a clear resource ('web page performance metrics') and enumerates the exact metrics measured (TTFB, FCP, LCP, DOM Content Loaded, Fully Loaded). This clearly differentiates it from sibling tools like check_mobile or check_links.

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 provides clear context for when to use the tool: when performance metrics and a performance score are needed, with support for mobile and desktop profiles. It does not explicitly name alternatives or exclusions, but no obvious sibling tool directly competes with it.

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