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

Annotations already declare readOnlyHint=true, idempotentHint=true and destructiveHint=false, so safety is covered. The description adds real behavioral context beyond that: the result is a frequency count 'over all of its ads in the library', clarifying the aggregation scope rather than a sample or single-ad view. It omits any pagination or result-size detail.

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 tight sentences, front-loaded with what is returned and its aggregation scope, with the parameter provenance tacked on second. No filler or redundancy.

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, the description must carry the return-value burden, and it does explain the shape of the result (hooks, hook mechanisms, angles with counts). Missing details such as paging, limits, or ordering keep it from being fully complete, but nothing critical is absent for calling it 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% and the single parameter is fully documented in the schema, so the baseline is 3. The description's note that advertiserId comes from search_ads rows largely repeats the schema's own wording, adding little new semantics.

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 and resource: returns an advertiser's most-used hooks, hook mechanisms and angles, aggregated as counts across all of its ads. This distinguishes it from sibling search_ads (raw rows) and get_ad (single ad), letting an agent tell it apart without opening a schema.

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?

There is no explicit when/when-not guidance or named alternative (e.g., winning_patterns). The one usage clue is the workflow linkage: 'advertiserId is the advertiser id shown in search_ads rows', implying you call search_ads first, but the selection criteria versus siblings is only implied.

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