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

Annotations already cover the safety profile (readOnly, idempotent, non-destructive, closed world), so the description correctly focuses on other behavior: it is a fixed reference dataset of ~250 countries returned in full with no pagination, and it explains the semantics of `availability: none`. That return-shape and value-interpretation guidance is genuinely beyond 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?

Three sentences, front-loaded with the resource, then the purpose, then the key caveat about `availability: none` and the return size. No filler and no repetition of the title.

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 compensates by stating the return cardinality (~250 countries) and that it is unpaginated, plus how to interpret the availability field. An agent has everything needed to call and use this tool.

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?

The tool takes zero parameters, so there is nothing for the description to disambiguate; the baseline for a parameterless tool applies.

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 resource and scope: traffic availability per country, a read-only reference lookup. It is trivially distinguishable from every sibling, which are all CRUD operations on labels, sites, proxies, templates, and traffic sources.

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 concrete use case – guiding a site's or template's location targeting – and implicitly frames when to consult it (before choosing targeting). It does not name an alternative tool or an explicit when-not condition, but no sibling overlaps this function, so the gap is minor.

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