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

Annotations already declare readOnlyHint, openWorldHint, idempotentHint, and destructiveHint false. The description adds minimal context ('official timetable data') but does not disclose behaviors like data freshness, rate limits, or any operational nuances. It does not contradict the 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?

A single, front-loaded sentence that conveys the core functionality without waste. It is appropriately sized for a tool whose parameters and safety are already documented in the schema and annotations.

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?

The tool has 5 parameters, but schema coverage is high and an output schema exists. The description explains the two modes (connections vs. departures) sufficiently, and the schema handles parameter details. Nothing critical for correct invocation is missing, though a sentence on typical use cases would strengthen it.

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 80%, so most parameters are already documented. The tool description adds the conceptual distinction between connections and departures, but this is also captured in the schema (destination: 'omit for a departure board'). Thus the description adds little beyond schema, warranting a baseline score of 3.

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 clearly states the tool provides Swiss public transport connections or next departures, using official timetable data. It names the specific resource (public transport) and the actions (connections or departures), distinguishing it from unrelated siblings like company_register or current_weather.

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 description implies usage for transport queries, but does not explicitly state when to use it versus alternatives. Since siblings are unrelated, the purpose is obvious, but there is no guidance on scenarios like planning a trip versus checking live departures, and no mention of when not to use it.

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