Metro train frequency

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

Annotations already declare readOnlyHint=true and openWorldHint=true, so the safety profile is covered. The description adds genuinely non-obvious behavioral context: coverage of the Wenhu line despite it having no timetable, and that results vary by day of week. It does not discuss caching, update cadence, or what happens for lines without frequency data.

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 dense sentences plus a one-line example, with the core measurement front-loaded before the coverage caveat and the sample invocation. Nothing is redundant with the title or schema.

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?

There is no output schema, so the description carries the return-value burden and does so by naming the payload fields (minutes between trains, peak vs off-peak, operating hours). With three fully documented parameters and read-only annotations, an agent has everything needed to call it correctly.

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 100%, with each parameter described and an enum for system, so the baseline is 3. The description reinforces the semantics with the TRTC/BR example and the day-of-week meaning of date, but adds no format or constraint detail 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?

States a specific resource and measurement: headway in minutes between trains by line, split into peak and off-peak, plus operating hours for a given day of the week. The note that it covers the Wenhu line 'which has no timetable' implicitly separates it from timetable-style siblings like bus_timetable or thsr_timetable, so an agent can pick it without opening the schema.

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?

The 'for a day of the week' framing plus the worked example (system "TRTC", line "BR") gives clear invocation context. It stops short of naming alternatives or exclusions, e.g. that first/last train times belong to metro_first_last_train even though operating hours are mentioned here.

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