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

Annotations already declare readOnlyHint, openWorldHint, and destructiveHint=false, so the safety profile is covered and the description adds real context on top: it discloses the computed signals returned, warns against fabricating hook_type/format, and constrains inputs to 'factual metadata'. It does not discuss cost, rate limits, or whether the brief depends on prior tool calls in the conversation.

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?

Three sentences, front-loaded with the usage trigger before the input rules and return summary. The trailing sentence listing return signals is slightly redundant given an output schema exists, but it is short and does not bloat the definition.

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 an aggregation tool sitting above the analyze_/search_ siblings, the definition covers the trigger, the required per-ad shape, the omit-if-unknown rule, and the shape of what comes back. Since an output schema exists, the description is not obliged to detail return values, and 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 100%, so baseline is 3, but the description earns above-baseline by explaining intent ('Pass factual metadata per ad') and the optionality rule for hook_type/format with an explicit anti-hallucination directive. The brands/context/conversation_id parameters are fully documented in the schema and the description sensibly does not duplicate them.

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 a specific verb-plus-outcome set (comparing brands, summarizing ad analysis, finding whitespace, producing takeaways) over 'analyzed ads across one or more brands', which clearly sets it apart from the search_* and analyze_ad_* siblings as a synthesis layer rather than a retriever. It stops short of naming those siblings, so an agent must infer the boundary itself.

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 a genuinely useful when-to-use enumeration (comparing brands, identifying winners, finding whitespace, surfacing patterns, takeaways/recommendations) and adds a negative constraint ('Omit hook_type/format if not derived from prior analysis — do not guess'). It never names an alternative tool or states when to prefer search_meta_ads_by_keyword or analyze_ad_video instead, so the routing is implied rather than explicit.

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