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

Annotations already declare readOnly, idempotent, non-destructive, open-world behavior, so the safety profile is covered. The description adds genuinely useful behavioral context beyond that: the data is live (delay, last reported position), the window is 90 minutes, and coverage includes DART and commuter services. No auth or rate-limit details, but the bar is lower given 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?

Three tight lines: purpose first, then when-to-use, then a concrete invocation example. Every sentence earns its place, though the return-field list is somewhat dense for the opening sentence.

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 does a good job enumerating returned fields (time, train, destination, delay, position). However, it leaves two of three parameters unexplained and gives no guidance on station code vs. name beyond a single name example, which is a meaningful gap for a 3-param 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 only 33%: 'station' is documented, but 'minutes' and 'results' are not explained anywhere. The description's 'within the next 90 minutes' implies a fixed window and could even mislead an agent away from the configurable minutes parameter, and the results limit is never mentioned. The example {"station":"Dublin Connolly"} only clarifies the station 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?

States a specific verb and resource ('Next train departures from one Irish station') with the time window and return fields (time, train, destination, live delay, position). It does not explicitly distinguish itself from siblings ie_find_station or ie_train_connections, though the departure-board framing makes the distinction inferable.

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?

'Use when: someone is at (or going to) a station in Ireland' gives a clear situational trigger. It does not name alternatives (e.g. ie_train_connections for journey planning) or state when this tool is the wrong choice, so it stops short of full routing guidance.

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