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

Beyond readOnlyHint/openWorldHint, it discloses the data provenance (public Ads Transparency Center), a hard result cap (up to 40 ads), and a cost model ($0.01 per result, no ads free) — all things annotations cannot convey. It doesn't cover pagination or failure behavior when a domain is unknown, so it stops short of a 5.

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 what you get, then the scope caveat, then the routing hint. Every sentence carries distinct information — data source, cost, and alternative — with no 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?

With an output schema present, return-value detail is unnecessary, and the description still covers cost, source, result cap, privacy scope and the alternative tool. For a 3-parameter read-only lookup with full schema coverage, nothing an agent needs before calling 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% and the schema already documents domain format, the region enum, and the context field, so the schema carries the load. The description only restates that region is an optional filter, adding no new semantics such as default region behavior or whether region also narrows the ad count estimate.

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 states a specific verb/resource ('Google Ads for a company domain') plus the exact data source (public Ads Transparency Center) and enumerates the return contents: advertising status, ad count estimate, up to 40 ads with format, dates and links. It is clearly separable from get_company_profile, which is named as the broader alternative.

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 gives an explicit use case ('public competitor advertising evidence'), an explicit exclusion ('does not access a private Google Ads account'), and an explicit alternative ('Use get_company_profile for combined research'). Nothing about when to select this tool is left to inference.

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