google_ads_ad_performance_compare

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

With no annotations supplied, the description fully discloses behavioral rules: INSUFFICIENT_DATA threshold for impressions < 100, tie-breaking (all top-score ads get WINNER), the score formula (ctr*cvr or ctr), and read-only nature. This goes well beyond structured annotations and gives the agent reliable expectations.

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?

The description is dense but every sentence carries essential information: purpose, verdict logic, return structure, read-only safety, and sibling alternatives. No filler or repetition; front-loaded with the primary function.

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?

Despite lacking an output schema, the description enumerates return fields and explains the scoring and verdict rules. It also states the read-only guarantee and differentiates from adjacent tools, making it self-sufficient for an agent to invoke 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?

Schema description coverage is 100%, so the baseline is 3. The description does not add syntax or format details beyond the schema, but the schema already provides rich guidance on ad_group_id, period, and customer_id. No further parameter explanation is needed.

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 uses the specific verb 'Rank' and clearly identifies the resource: 'ENABLED ads within a single Google Ads ad group' while assigning verdicts. It is unmistakably distinct from sibling tools like google_ads_ad_performance_report and google_ads_rsa_assets_analyze, which are explicitly called out as alternatives.

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?

Provides explicit context for use: it scopes comparison to a single ad group and is read-only. It names alternatives for cross-ad-group reporting and RSA asset-level analysis, giving clear when-to-use and when-not-to-use guidance.

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