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

With no annotations, the description must carry behavioral context; it does indicate the tool is a read-only listing operation and mentions that it uses the same key as kuongeo.com's /api/here. However, it does not disclose error behavior, rate limits, or whether valid codes are required, leaving some behavioral ambiguity.

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?

The description is short and front-loads the core function and code format. The second clause about the shared key is useful but somewhat cryptic, so the text is concise without being perfectly polished.

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?

The tool is simple (one parameter, no output schema), and the description covers the main purpose and parameter. Still, it does not describe the structure of the returned list, possible empty results, or error cases, and it gives no context for choosing this tool among many siblings.

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 schema only defines 'code' as a string with no description, but the tool description adds that it must be a 5-digit municipality code (自治体コード5桁). This is the essential semantic for the single parameter, though it does not give examples or format details such as leading zeros.

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?

The description states that the tool returns the list of return gifts (返礼品) for a municipality identified by a 5-digit code. This is a clear resource-and-output statement, though it lacks an explicit verb and does not differentiate from related siblings like furusato.

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 guidance is given about when to use this tool instead of a sibling, and no alternatives or exclusions are mentioned. The only usage hint is implied by the purpose: use it when you have a 5-digit municipality code and need its return-gift list.

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