High speed rail timetable

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

Annotations already cover the read-only and open-world aspects, and the description adds real value on top: the four-week data horizon and the 'from now on for today' default scoping behavior. It also enumerates the returned fields, though it says nothing about result ordering, pagination, or empty-result behavior.

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 short sentences, front-loaded with the core capability, then the coverage constraint, then a compact example. No sentence is redundant and nothing buries the key information.

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 usefully names the returned attributes and the data horizon, which is what an agent needs to interpret results. It could still say what happens when a date is beyond the four-week window or when no trains remain after the given time.

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%, so the schema already documents every parameter including station name/ID alternates and defaults. The worked example (台北/左營/2026-10-23/08:00) illustrates valid value forms, but that is reinforcement rather than new semantic detail, so the baseline 3 applies.

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 gives a specific verb and resource: THSR trains between two stations on a given day, and names the fields returned (departure, arrival, travel time). It is clearly distinct from fare or live-board siblings, though it never explicitly contrasts itself with thsr_train or rail_station_departures, which sound adjacent.

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 states the usable time window precisely: 'from now on for today' and 'TDX covers about four weeks ahead', so an agent knows the valid date range and the default starting point. It does not name an alternative tool for out-of-range dates or for seat availability, so the guidance stops short of explicit when-not/alternatives.

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