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

Annotations already declare readOnlyHint, idempotentHint, non-destructive and closed-world, so the safety profile is fully covered. The description adds one genuinely useful behavioral detail — that monetary values are in minor units (cents) — and clarifies the result granularity, but says nothing about timezone, date-range edges, or whether results are cached/lagged.

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?

Very compact — one sentence plus a units note — and the purpose ('How the ads did') is front-loaded, with the metric list immediately after. The phrasing is informal and the second sentence is a fragment, which slightly undercuts clarity but wastes no words.

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 only two optional parameters, complete annotations, and an output schema present, the description does enough: it tells the agent the aggregation levels and the currency unit. The notable remaining gap is sibling differentiation, which is what keeps this from a 5.

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 100%, with both parameters documented including the 1–90 day range and the omit-for-all semantics. The description's reference to 'each campaign' only loosely hints at the campaign_id filter, so it adds little beyond the schema — 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?

States the resource (ad results) and enumerates the exact metrics returned — spend, impressions, clicks, results, CTR, CPC, cost per result — at three levels of aggregation (totals, per campaign, per ad). It does not, however, distinguish itself from siblings like get_performance or ads_overview, leaving the agent to guess which report tool to pick.

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?

No statement of when to use this versus get_performance, ads_overview, get_ad_campaign, or list_ad_campaigns, and no mention of the default 7-day window or when to narrow with campaign_id. The only routing clue is implicit in the phrase 'each campaign and each ad'.

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