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

Annotations already declare readOnlyHint, idempotentHint, and destructiveHint=false, so safety is covered. The description adds value by disclosing the shape of each returned record (key, Korean name, seller count), which matters because there is no output schema. It does not mention ordering or result size, which is a minor gap.

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 short sentences with the core content front-loaded. The Korean sentence largely restates the English rather than adding information, which is mild redundancy, but it is plausibly intentional for a bilingual audience and costs little.

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 zero-parameter, read-only lookup tool with full annotation coverage, the description supplies the one thing structured data cannot: what each entry contains. No output schema exists, and the field list compensates adequately. Ordering/pagination details would be the only remaining nicety.

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 the baseline of 4 applies. The description's field listing describes return values rather than inputs, which is appropriate here and adds no confusion.

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 clear verb (list) and resource (destination countries covered) and even enumerates the returned fields (key, Korean name, seller count). It implicitly distinguishes itself from compare_countries by being the enumeration source rather than a comparison tool, but never names that relationship explicitly.

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?

No when-to-use guidance is given. With siblings like compare_countries and find_esim_prices that likely consume country keys, the description should say this is the tool to call first to discover valid keys, but it offers no routing or exclusions.

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