Get stop 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 of behavioral disclosure. It establishes that this is a getter/read operation but does not explain what 'factual' means in practice, what time range is covered, whether delays/cancellations are included, or what the response looks like. The description is not misleading, but it is too thin to be transparent.

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 extremely concise: one short sentence with no filler. Key information is front-loaded. The only deduction is that 'factual' is an unusual modifier that is not elaborated anywhere, so it arguably does not fully earn its place in such a terse definition.

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 a single integer parameter and no output schema, the description leaves critical questions unresolved: what arrival data means (scheduled vs real-time vs historical), what time period is covered, and what fields are returned. The presence of sibling get_vehicle_forecast suggests a distinction, but this description does not clarify it. An agent would be uncertain how to interpret the response.

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 covers 100% of the one parameter, stationId, including type, range, and a description. The tool description adds no parameter-specific meaning beyond the schema, so the baseline score of 3 applies. The description's 'factual' wording could relate to the stop context but does not clarify the parameter format.

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 a clear verb and resource: 'Get factual arrival data for a stop.' The word 'factual' hints that this is actual observed data rather than a forecast, which distinguishes it from sibling get_vehicle_forecast. However, 'factual arrival data' is not formally defined, leaving some ambiguity about whether it means scheduled, real-time, or historical arrivals.

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?

There is no guidance about when to use this tool versus alternatives such as get_stop_routes, get_vehicle_forecast, or get_stop_vehicle_forecast. The agent must infer usage entirely from the tool name and the vague 'factual' cue. No explicit when-to-use or when-not-to-use context is provided.

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