Train / trip details with live delay

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

Annotations already declare readOnlyHint=true and openWorldHint=true, so safety and external-data exposure are covered structurally. The description adds that results include live delays and cancellations, which is useful behavioral context about data freshness, but it says nothing about error behavior, ambiguity handling, or rate limits.

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 sentences: the first front-loads what the tool returns, the second explains how to identify the trip. No filler, and the most decision-relevant information (output contents) comes first.

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, the description correctly carries the burden of describing the return payload (stops, times, platforms, live status). It does not address what happens if neither `ref` nor `train` is supplied, nor the meaning of the `live` flag, leaving minor gaps for a zero-required-parameter tool.

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 coverage is 75%, so the schema already documents `ref`, `date`, and `train`. The description still adds value: it explains where `ref` comes from and gives accepted train formats ('3510', 'IC 3510', 'Podhalanin'), clarifying matching semantics. The `live` boolean remains undocumented in both places, which caps this below 5.

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 names a specific resource (all stops of one train/bus run) and enumerates the returned fields (times, platforms, live delays/cancellations), so the agent immediately knows what this returns versus the summary-level sibling tools. It also points at plan_journey/departures as the origin of the `ref`, distinguishing it from those tools.

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 gives two concrete ways to identify the trip — by `ref` from plan_journey/departures, or by train number/name plus date — which is real invocation guidance. It stops short of stating when *not* to use it (e.g., for journey planning, use plan_journey), so it lacks explicit exclusions.

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