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

Annotations already declare readOnly, idempotent, non-destructive and open-world, so the safety profile is covered. The description adds no behavioral context beyond the annotations — nothing about date-range defaults, timezone handling, required property scoping, or result granularity for what is otherwise a fixed-shape 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?

Two short sentences, front-loaded with the metric list and followed by the insight framing. No padding, though the second sentence is slightly promotional rather than informative.

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 simple read-only report with no output schema, stating metrics and breakdown dimension is a reasonable minimum. However, with no date-range behavior, no property-format reminder, and no result shape, an agent still needs the schema to call it correctly.

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?

Three parameters with only 33% schema description coverage, and the description says nothing about any of them. It never mentions the required property id or the startDate/endDate range, so the two date parameters are undocumented in both schema and description.

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 specific metric outputs (earnings, page views, RPM, CTR) and the breakdown dimension (desktop, high-end mobile, tablet), which cleanly distinguishes it from siblings like ads_device_performance and gsc_device_country_breakdown. The verb is implicit but the resource and scope are unambiguous.

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 phrase 'Reveals mobile monetization gaps' hints at when the report is useful, but no alternative tool is named and no condition for choosing this over adsense_report, adsense_daily_trend, or ads_device_performance is given. Guidance is left entirely to inference.

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