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

Annotations already mark it read-only/idempotent, and the description goes well beyond them: it explains that short windows on paused campaigns return zeroed rows that look like missing data, that Google reports impressions from an earlier date than clicks/cost so lifetime impressions can exceed a full-spend window, that CTR is comparable only within the same window, and that NOT_APPLICABLE grades are common and summarized. This is genuinely useful operational context.

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?

Front-loaded with the headline purpose and the deciding metric, then organized by parameter and caveat. It is long but nearly every sentence carries distinct information; minor redundancy in re-emphasizing lifetime vs window keeps it from a 5.

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 5-parameter report tool with an output schema and full annotations, the description covers all parameters, default semantics, edge cases, and caveats. Nothing an agent needs to call it correctly is missing.

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 0%, so the description must carry the burden, and it does: days (0=lifetime, 7/14/30, any other becomes an explicit range reported as period_from/period_to), limit (cap with true total always reported), min_impressions (drops low-data assets), and campaign_id (empty = whole account). Only customer_id is left implicit, which is self-evident.

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?

Names a specific resource (RSA asset report) and enumerates the exact metrics returned at HEADLINE/DESCRIPTION level, plus Ad Strength. This clearly separates it from sibling report tools like get_report, performance_report, and from update_rsa which mutates rather than reports.

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?

States the decision context explicitly ('evidence for deciding which headlines to keep and which to replace') and recommends days=0 for keep-or-drop. It does not name sibling alternatives (e.g., get_ad_details or update_rsa) or state when NOT to use it, so it falls short of a 5.

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