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

No annotations exist, so the description carries the full burden. It does disclose the return contents (codes, JP/EN names, data caveats), which is genuinely useful. It says nothing about output format, whether results are paginated or cached, or how the returned codes are meant to be consumed downstream.

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, front-loaded with what is returned and followed by the usage recommendation. No filler. The phrasing is slightly vague ('間違えにくい') but earns its place as actionable guidance.

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 and no annotations, the description must supply the shape of the result, and it only sketches it (codes, two name languages, caveats). Critically, it never says the codes are the input vocabulary for sibling tools such as get_trade, which is the main reason an agent would call this first.

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 no parameter semantics to explain; baseline 4 applies. The description correctly implies a parameterless enumeration rather than a lookup requiring input.

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 (returns/使える) and resource: available item codes plus names in Japanese and English, plus data caveats. That is more than a restatement of the name 'list_codes'. It does not, however, connect itself to the sibling family (get_trade, top_partners, yearly_series), so an agent cannot tell from the description whether 'code' means commodity codes for trade statistics.

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 explicit sequencing guidance: call this first and you are less likely to make a mistake. That is a clear when-to-use signal, which is rare. It stops short of naming alternatives or saying what to do once the codes are retrieved.

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