cwv_report

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

No annotations are provided, so the description carries the full burden of behavioral disclosure. It reveals nothing about data source (CrUX field data vs. synthetic measurement), what 'comprehensive' means (which metrics: LCP, INP, CLS), whether it performs external API calls subject to rate limits, how includeHistory alters behavior, or the format/latency of the report.

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 sentence with no filler, front-loading the core action and resource. It is appropriately terse for a two-parameter tool, though the brevity does contribute to the under-specification penalized in other dimensions.

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?

With no output schema, no annotations, and a sibling cluster of performance tools (crux_query, crux_history, psi_analyze, lighthouse_audit), the description should do more to contextualize what the report contains and how it differs. An agent cannot determine whether this is the right tool for field-data CWV analysis, historical trends, or lab audits.

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 50%: the 'url' parameter is documented in the schema, and 'includeHistory' is self-explanatory from its name. The description adds little parameter-level insight beyond 'for a URL', which merely echoes the schema, but it does not actively mislead and the parameter meanings are reasonably inferable.

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 states a specific verb ('Generates'), a resource ('Core Web Vitals report'), and a target ('for a URL'), so the agent knows what the tool produces. However, it does not distinguish itself from performance-related siblings such as psi_analyze, crux_query, crux_history, or lighthouse_audit, which an agent could reasonably confuse it with.

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?

There is no guidance on when to use this tool versus the many overlapping performance and monitoring siblings. The description does not mention data source differences (e.g., field data from CrUX vs. lab data), speed, or any conditions under which an alternative would be preferable.

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