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

Annotations already declare readOnlyHint=true, destructiveHint=false, and openWorldHint=false, so "No writes or access grants" largely restates structured data. The one piece of genuine added context is the refusal behavior for restricted services, but it is vague — it doesn't say what the error looks like, which services are restricted, or what "fresh server-verified access" requires operationally.

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 short sentences, front-loaded with the core action, with no filler or repetition. The only cost is that brevity comes at the expense of clarity ("bounded native"), not verbosity.

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?

An output schema exists, so return values need not be explained, and annotations cover the safety profile. However, with nested parameters at 33% coverage and no differentiation from the reach/benchmark siblings, an agent still lacks what it needs to call this correctly and confidently.

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 only 33% — only customer_id is documented — and the nested body.location_id plus the connection_context pattern are undocumented in both schema and description. The description mentions no parameters at all, so it does nothing to compensate for the low coverage on a nested-object schema.

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?

It states a verb (read) and a resource (native reach_products insight), so the general shape is clear, but "bounded native" is unexplained jargon and the description never distinguishes this from the adjacent reach tools (google_ads_reach_forecast, google_ads_reach_locations, google_ads_benchmark_products). An agent can guess it reads product-reach data but cannot confidently pick it over its siblings.

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?

"Restricted services require fresh server-verified access and otherwise refuse" is a precondition/failure note, not guidance on when to choose this tool. No when-to-use, when-not-to-use, or named alternative among the several reach/benchmark siblings is given.

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