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

Annotations already declare read-only, idempotent, non-destructive behavior, so safety is covered. The description adds useful return-content context: countries, selectable network counts, and the starting-price basis (1 GB, 7 days, cheapest network). It does not mention pagination or whether all countries are returned at once.

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?

Two sentences with no filler. The first front-loads what the listing contains, and the second gives use cases; the parenthetical pricing basis is informative rather than 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?

There is no output schema, so the description must explain return values, and it names the key fields and pricing basis. Combined with annotations covering safety and schema covering parameters, it is adequate, though it does not fully describe the response shape.

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 bucket, currency, and language are already documented in the schema. The description adds no parameter-specific semantics, but the baseline is 3 because the schema does the heavy lifting.

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 the resource clearly: every country variotrip can route, plus the returned metrics (selectable network count and starting price). It is distinguishable from sibling tools like get_networks and price_grid by being a country-coverage list, though it does not explicitly name those alternatives.

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?

Explicitly says to use it to check coverage or to see which countries of a trip are available. This gives clear usage context, but there are no explicit exclusions or guidance pointing to siblings for network or price detail.

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