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

The description explicitly says 'Read-only', which matches the readOnlyHint annotation and adds no contradiction. It adds the 'Pro' access qualifier, but does not disclose other behavioral traits such as default date ranges, result volume, rate limits, or the Meta breakdown-combination constraint that appears only in the schema.

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?

Two short sentences plus the 'Read-only. Pro.' fragments are efficient and front-loaded with the main purpose. There is no filler, though the 'Pro.' fragment is slightly ambiguous without additional context.

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?

Given no output schema and 7 parameters, the description is enough for basic invocation with breakdowns, but it omits important operational details such as date format/defaults, limit behavior, and output shape. The schema carries the Meta-specific breakdown-combination rule, so the description alone would not be fully sufficient.

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?

The description translates the raw enum breakdown values into understandable segments (placement, device, age, gender, region, hour-of-day), adding practical meaning. Schema description coverage is 57%, and the description does not compensate for undocumented parameters like since, until, or limit, so its added value is modest.

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 and resource ('Break performance down by segment') and enumerates the exact segment dimensions, which clearly distinguishes it from generic insight tools like get_insights. It does not explicitly name a sibling, but the scope is concrete and not a tautology.

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 phrase 'to find wasted spend or a fatiguing audience' gives a clear use case and implies when this tool is valuable. However, it does not explicitly say when not to use it or which sibling alternative to choose (e.g., get_insights for raw trends), leaving sibling differentiation to inference.

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