Ads reach forecast

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

Annotations already declare readOnly, idempotent, open-world, non-destructive, so safety behavior is covered. The description adds that the return includes a reach curve and on-target impressions, which is meaningful context beyond the annotations. It says nothing about latency, quota cost, or whether the forecast is deterministic across currency changes.

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 front-loaded sentence with no filler; the core noun phrase (forecast plus its two outputs) comes first, then the inputs. Telegraphic list style is dense but readable. Minor cost: the terse 'products [{code, budget_micros}], location, currency, duration' reads like schema echo rather than guidance.

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, the description need not explain return values, and annotations cover safety. The remaining gap is input sourcing and units for a 5-required-parameter tool at 0% schema coverage. Adequate to start a call, but an agent may guess at currency format or duration semantics.

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 0%, so the description must carry parameter meaning, and it partially does: it names products with {code, budget_micros}, location, currency, and duration. However, customer_id goes unmentioned, the products item schema is open (additionalProperties true) with only two hinted fields, and units (micros, days) are implied rather than explained.

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+resource: a Reach Planner forecast of reach curve and on-target impressions for a media plan. This clearly separates it from the sibling lookups ads.reach.locations and ads.reach.products, which supply inputs rather than forecasts. Slightly compressed phrasing ('Reach Planner forecast for a media plan') but the purpose is unmistakable.

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?

No when-to-use or when-not-to-use guidance, and no mention of prerequisites. The two obvious siblings, ads.reach.locations and ads.reach.products, almost certainly supply location_id and product codes for this call, but the description never says so. An agent must infer the workflow entirely.

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