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

With no annotations, the description carries the full burden of behavioral disclosure. It states the tool returns a list of city codes, which implies a read-only operation, but does not describe the response format, whether the list is static, or any limitations. This is a minor gap for such a simple tool, but the description does not contradict annotations.

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 a single, efficient sentence that immediately states the purpose. There is no wasted text, and the core function is front-loaded. This is exemplary conciseness for a tool with no parameters.

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?

Given the tool's low complexity (no parameters, no output schema), the description is reasonably complete. It tells the agent exactly what the tool provides (a list of city codes) and their context (for bus info). It could mention whether city names are included, but that is a minor omission.

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 has zero parameters, so the baseline is 4. The description correctly notes the absence of parameters by having an empty schema, and there is nothing else to document. The description adds no parameter details but does not need to.

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 clearly states the tool provides a list of Korean city codes for city bus information. It specifies the resource (city codes) and their purpose, which distinguishes it from siblings like korea_bus_stops (bus stops) and korea_area_codes (area codes). However, it does not explicitly name these siblings or contrast with them, so it misses the top score.

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?

The description implies the tool is used to retrieve city codes needed for bus information, but it does not explicitly state when to use it versus alternatives or mention any exclusions. For a simple list tool, this is adequate but lacks explicit routing guidance.

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