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

Annotations already declare readOnlyHint, idempotentHint and openWorldHint, so the safety profile is covered. The description adds useful context about which metric families come back, but says nothing about auth requirements, rate limits, or whether data is fresh/aggregated.

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 tight sentences, metric list front-loaded, no filler. Every clause adds information.

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 the description usefully enumerates the returned metric families, but for a report tool it omits date-range behavior (defaults, timezone, max span) and any sense of output granularity, leaving real gaps 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?

Schema coverage is only 33% – property is documented (with a pointer to list_properties) but startDate and endDate carry no description beyond a date regex. The description mentions no parameters at all, so it does not compensate for the uncovered date-range inputs or their defaults.

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?

States a specific verb+resource (search impression share per campaign) and enumerates the exact metrics returned (lost to budget, lost to rank, top-of-page, absolute-top). This is far more precise than generic siblings like ads_campaign_performance, though it never names an alternative to route against.

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 closing clause 'Shows where more budget or better ads would unlock volume' implies the diagnostic use case, but there is no explicit when-to-use versus ads_budget_pacing or ads_campaign_performance, and no stated prerequisites or exclusions.

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