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

Annotations already declare this a safe, read-only, closed-world call, so the description doesn't need to re-establish that. It adds two things structured fields don't: an entitlement prerequisite (Pro plan) that will cause failures if unmet, and a return-shape detail ('money also listed per currency in byCurrency') that an agent can use to interpret the response.

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 that leads with the verb and the metric list, then the optional filter, then the prerequisite. Dense but every clause carries information; the parenthetical date-range note is slightly awkwardly embedded but not wasteful.

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 must convey return contents, and it does so by listing the metrics and the byCurrency breakdown. Gaps remain around aggregation granularity and the default period when no range is given, but nothing essential for a correct call is missing.

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 both params are documented as ISO dates, so the baseline is 3. The description only adds that the range is optional and that 'from'/'to' form a pair; it doesn't state what happens when only one bound is supplied or what default window applies when both are omitted.

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?

Names a specific verb ('Get aggregate stats') and resource ('for the brand') and enumerates the metrics returned (revenue, commissions, conversions, clicks), which distinguishes it from the list_* siblings that return raw records. It does not explicitly name a sibling alternative, but the aggregate framing is clear enough that an agent won't confuse it with list_conversions or get_program_overview.

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?

Gives a real usage gate ('Requires Pro plan or higher') and clarifies that the date range is optional, so an agent knows it can call this with no arguments. No explicit when-not or named alternative, which keeps it short of a 5, but the context is sufficient to decide whether and how to call it.

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