Real-time subway arrivals

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

No annotations are provided, so the description carries the full burden. It discloses input formatting rules (omit '역' suffix, use '서울' for '서울역') and offers a Korean usage example, which is useful. However, it does not disclose error behavior (e.g., unknown station) or response format, leaving some ambiguity for a tool that likely returns real-time data with limited context.

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-loaded: the English purpose statement comes first, followed by a usage hint in English, then the same information is repeated in Korean along with a sample query. The repetition is somewhat redundant (English and Korean say similar things), but the overall length is appropriate and each sentence contributes to usability.

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 (two params, no output schema). The description covers the core purpose and input format but omits what the response looks like (e.g., next train times, directions, count). Given no output schema, the description could have disclosed return value structure or note that data is real-time and may vary. It is adequate for invocation but not fully complete for setting expectations.

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 description coverage is 100% (both station and limit are described). The description adds an English-language rule about omitting the '역' suffix and gives an explicit example ('강남'), which complements the Korean schema description. It also clarifies the station parameter's intended value in a way that is accessible to non-Korean speakers, adding meaningful semantic context beyond the schema.

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 starts with a clear verb and resource: 'Get real-time subway train arrivals for a Seoul station.' This precisely states the tool's function and distinguishes it from siblings like get_subway_ridership (ridership statistics vs. live arrivals). The added example and Korean usage hint reinforce specificity.

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?

It provides concrete guidance: 'Pass the station name WITHOUT the "역" suffix if possible (e.g. "강남").' and includes a sample query in Korean ("2호선 강남역 열차 언제 와?") to indicate the intended use case. While it does not explicitly list alternatives or when-not-to-use, the real-time scope and contrast with siblings like get_subway_ridership imply appropriate usage.

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