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

Annotations already mark this as a read-only, open-world tool. The description adds useful behavioral context beyond annotations: it discloses that calls cost 2 credits, that paging uses a cursor from the previous response, and that results include first-shown and last-shown dates.

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 compact and front-loaded, moving from purpose to scope, paging, cost, and required inputs. There is minor redundancy between the first two sentences, but no significant waste.

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 available, the description does a reasonable job of explaining the return context by mentioning creatives and first/last-shown dates. It also covers pagination and cost, though it does not describe the full response shape or the `cache_max_age` parameter.

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 high, so most parameters are already documented. The description adds an important cross-parameter constraint not enforced by the schema: pass either `domain` or `advertiser_id`. It also clarifies cursor pagination, though `cache_max_age` remains undocumented in both places.

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 clearly states the resource and scope: creatives from the Ads Transparency Centre for one advertiser id or one verified domain. It is more specific than the title alone, though it does not explicitly name sibling tools like google_ad or google_adLibraryAdvertisers to sharpen the distinction.

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?

It states that either `domain` or `advertiser_id` must be passed and explains cursor-based pagination. However, it gives no guidance on when to choose domain versus advertiser_id, nor when to use this tool instead of nearby siblings such as google_ad or google_adLibraryAdvertisers.

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