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

Annotations already declare readOnly, idempotent, non-destructive and closed-world, so safety is covered. The description adds genuinely useful behavioral context by defining the price basis (1 GB, 1 day, cheapest network), which prevents misreading the 'starting price'. It omits pagination/size limits, which keeps it below 5.

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?

One sentence describing contents plus one sentence on usage; zero filler and the price-basis qualifier is included exactly where it prevents ambiguity.

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 usefully sketches the return shape (country, network count, starting price basis), and the schema handles the inputs. Only the absence of result-size or freshness details keeps it from being fully complete for a list 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?

Schema description coverage is 100%, so bucket, currency and language are fully documented in the schema, including the default-from-language behavior. The description adds no parameter meaning beyond that, making the baseline 3 correct.

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 verb+resource ('List destinations') and what each row contains (countries, selectable network count, starting price with its 1 GB / 1 day / cheapest-network basis). It distinguishes itself functionally from single-country pricing siblings, but never names a sibling to route against.

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 clear usage context: 'check coverage or compare many countries at once,' which implies a survey/browse intent versus the per-country quoting tools. No explicit when-not-to-use or named alternative (e.g. price_grid, quote_esim) is given.

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