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

Annotations already declare readOnlyHint=true, idempotentHint=true, destructiveHint=false and openWorldHint=false, so 'Read only' largely restates structured data. The genuinely additive phrase is 'saved data,' which signals the results are a stored snapshot rather than a live computation, plus the note that audiences are flagged for delivery viability. No permission requirements or refresh/freshness semantics are spelled out.

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?

A single sentence that front-loads the core purpose ('Get the audience picture') before enumerating the return contents. It is dense and slightly list-like, but no sentence is wasted and the most important information comes first.

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 carries the burden of describing returns and does so thoroughly (audience sizes, delivery viability, placement splits). Combined with annotations covering the safety profile and a fully documented single parameter, an agent has enough to call this correctly; only data freshness is left to inference.

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 100%, and the single brand_id parameter is fully documented in-schema including the fallback to the most recently updated brand. The description adds nothing about the parameter, so the baseline 3 applies.

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 uses a specific verb (Get) plus resource (audience picture) and enumerates the concrete contents returned: buyers in the period, saved custom audiences with size and deliverability, and results split by placement. It distinguishes the payload from neighbors like get_performance or get_sales_funnel by naming audience- and placement-specific data, though it never names an alternative tool explicitly.

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?

There is no when-to-use guidance and no routing to or away from siblings such as get_performance or get_sales_funnel. The only contextual cue is 'Read only, saved data,' which describes the data nature rather than the conditions under which this tool is the right choice.

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