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

Adds real context beyond the readOnly/openWorld annotations: the response includes every rendering variant plus per-country run dates, and the cost is explicitly 1 credit. The explanation of where headline/body/linkUrl come from is useful provenance detail, though nothing is said about failure modes for invalid or expired creatives.

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 tight sentences, front-loaded with the core scope, then the result shape, then cost. No filler or repetition of the title.

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 does the necessary work of explaining what comes back (variants, run dates, rendered text-ad fields). Only the undocumented cache_max_age parameter and the absence of error behavior keep it from being fully complete.

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 only 67%, and cache_max_age is undocumented in both schema and description. The description adds nothing about the url format or how region overrides the URL's region parameter, so it does not compensate for the coverage gap.

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+resource: fetches a single creative from the Ads Transparency Centre, with rendering variants and per-country run dates. The 'one creative' framing distinguishes it from list-oriented siblings like google_advertiserAds and google_adLibraryAdvertisers.

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?

Implies you pass a creative URL obtained elsewhere, but never states when to use this versus google_advertiserAds or google_adLibraryAdvertisers, nor any prerequisites for obtaining the URL. Usage is inferable from the schema example but not spelled out.

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