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

The annotations already declare readOnlyHint, openWorldHint, idempotentHint, and non-destructive behavior, so the safety profile is covered. The description adds valuable behavioral context beyond the annotations: latest available month, maximum 10 rows, field names, and fixed worldwide scope. No contradiction with annotations is present.

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 two concise sentences with no filler. The core output and constraints are front-loaded, and every clause adds information: time period, row cap, fields, coverage, and parameter restriction.

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 low-complexity single-parameter tool with a rich output schema and strong annotations, the description is fully sufficient. It covers the relevant behavioral constraints and return-shape details without requiring an agent to open the schema or infer hidden limitations.

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% for the single required `domain` parameter, so the baseline is already covered. The description adds extra semantic value by clarifying that a country parameter is not accepted and that the fixed worldwide scope is part of the endpoint's behavior.

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 resource (a domain's traffic) and the specific metric (top countries by share for the latest available month), and specifies the returned fields and row limit. It also distinguishes this endpoint from alternatives by stating that geography coverage is worldwide and fixed, with no country parameter accepted.

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 clear context for invocation: it returns country-level traffic share for the latest month and explicitly tells agents that a country parameter is not accepted, implying this tool is for worldwide breakdowns rather than country-filtered reports. It does not name a specific alternative tool, but the exclusion is clear enough.

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