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

Annotations already declare readOnlyHint, idempotentHint, destructiveHint=false, and openWorldHint, so the safety profile is covered. The description usefully adds the default time window (last 30 days) and sort order (by cost), which are behavioral traits not in the annotations, but omits pagination behavior for limit and any auth/permission notes.

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 compact sentences with the metric list front-loaded and defaults trailing. There is minimal waste, though the bare column enumeration leans toward inventory rather than instruction.

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, listing the returned metrics is genuinely helpful, and the default window/sort add context. But for a 5-parameter tool with 20% schema coverage, the description leaves the campaign filter, limit cap, and date format unexplained, and gives no alternative-tool guidance.

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 only 20% (just 'property'), leaving limit, startDate, endDate, and campaign undocumented. The description touches date defaults ('last 30 days') but adds no meaning for limit, campaign filtering, or the date pattern, so it does not compensate for the low coverage.

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 names the resource (keywords) and enumerates the returned metrics (match type, quality score, cost, clicks, conversions, CPA, impression share), so an agent knows this is a keyword-level performance report. However, there is no explicit verb and no differentiation from closely related siblings like ads_search_terms, ads_quality_score_audit, or ads_campaign_performance.

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 only usage-relevant statement is 'Default last 30 days, sorted by cost,' which describes default behavior rather than when to choose this tool over alternatives. No when-to-use, when-not-to-use, or sibling routing guidance is provided despite many overlapping ads_* tools.

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