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

Annotations already declare readOnlyHint and openWorldHint, so the safety profile is covered. The description adds genuinely useful non-schema behavior: a $0.002 USDC charge per successful call via x402 on Base/Solana/Arc, with failed calls not billed. It does not cover pagination or how the approximate total ad count relates to the limit parameter.

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?

Front-loaded with the data source and the two modes, and the pricing clause is placed last. It is dense with parenthetical field lists that partially duplicate the output schema, which costs a little efficiency but nothing is misleading or wasted on filler.

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?

Output schema exists, so the enumerated return fields are redundant but harmless; the description still supplies the mode selection, optional region filter and payment model an agent needs. The only real gap is no mention of pagination or how limit interacts with the approximate ad count.

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 the schema already documents all five parameters and the baseline is 3. The description adds value by mapping parameters to outcomes — name/domain for advertiser search versus advertiserId/domain for ad listing, and region as an optional country narrowing — which the flat schema does not connect.

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 (Google Ads Transparency Center) and enumerates the two distinct modes: advertiser lookup by name/domain and ad listing by advertiserId/domain. An agent can tell exactly what the tool returns, including fields like creative ID, format, shown dates and preview URL.

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?

The description makes the mode split explicit (search advertisers vs. list ads) and notes the region filter is optional, which is enough to pick the right parameter. It never names a competing tool or states when-not-to-use, so an agent must still infer that this is the right choice versus seo_linkedin_ad_library or the general news/search siblings.

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