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

With no annotations, the description carries the burden of behavioral disclosure. It adds context about ad spend vs Stripe purchases and USD estimates at 100 credits=$1. Still, it does not disclose the return format, whether results are paginated, or what happens when campaign_id is omitted. This is acceptable for a read-focused report but not rich.

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?

The description is one dense sentence that front-loads the core purpose and uses a sibling reference to avoid repeating field definitions. The '[Buy]' prefix is enigmatic but not distracting. Overall, every piece earns its place without wordiness.

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 there is no output schema, the description points to get_advertiser_report for money fields, which helps define expected return values. However, it doesn't explicitly describe how 'breakdown by campaign' appears in the response or how period modes map to date parameters. The schema covers parameters, but the description relies on sibling context for full understanding.

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%, so the schema fully documents all 8 parameters. The description repeats the period enum and notes campaign_id is optional, adding no new meaning beyond what the schema already provides. It does not clarify how the date parameters (date, month, start/end, week_start) interact depending on period.

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 clearly states 'Advertiser period breakdown by campaign' with 'same money fields/legend as get_advertiser_report,' specifying the exact resource (advertiser report) and scope (per-campaign). The name itself also distinguishes it from sibling tools like get_advertiser_report by_placement.

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 references get_advertiser_report as the baseline for money fields/legend, implying this tool is used when a campaign-level breakdown is needed. The period enum is shown, and campaign_id is noted as optional. However, it does not explicitly state when NOT to use this tool or mention the by_placement alternative.

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