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

Annotations already cover read-only, idempotent, and non-destructive behavior. The description adds useful context that all four cuts share the same period and that omitting `by` returns all four, but it does not describe pagination, output formatting, or other behavioral caveats. There is no contradiction with the annotations.

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 three sentences with no wasted words. The first defines the resource, the second grounds it in realistic use cases, and the third states the key parameter behavior. It is compact, readable, and every sentence earns its place.

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?

For a read-only tool with two optional enum parameters, this is nearly complete: it states the grouping dimensions, the default behavior, and the intended use cases. It does not explicitly describe the exact return shape or mention the `range` parameter, and there is no output schema to fill that gap, so some inference is still required.

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 baseline is 3. The description adds value beyond the schema by mapping `by` values to concrete analytic questions, such as department to 'which team is most at risk' and language to Dutch-speaker click behavior. It also clarifies the default of returning all four cuts; the `range` parameter is left to the schema, which documents it well.

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 identifies the tool's resource and scope: it produces breakdowns of the same period by department, template, language, and campaign. It also uses concrete example questions to communicate intent. It does not explicitly differentiate from sibling tools, so it stops short of a 5.

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 description gives explicit usage guidance for the `by` parameter: ask for one cut with `by`, or omit it for all four. It also signals what kinds of questions this tool answers, which helps an agent decide when to use it. It does not mention alternatives or when not to use it, so it is not a 5.

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