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

Adds meaningful context beyond annotations: live schedules include delays/cancellations only for departures within 30 min, name resolution happens internally, and return fields are listed. This complements the readOnlyHint=true and idempotentHint=true annotations without contradiction.

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?

Four sentences, purpose first, no filler. Each sentence adds value: purpose, input handling, return contents, and live data caveat.

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?

No output schema exists, so the description appropriately details return values (departure/arrival, duration, transfers, trip IDs). It covers key behaviors like live data and internal name resolution. However, it does not mention how to get more connections or pagination limits, leaving a slight gap given the sibling get_more_connections.

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%, so baseline is 3. The description adds little beyond the schema: it mentions 'station names or UIC IDs' for from/to, but the schema already provides examples. No additional parameter meaning is given.

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 opens with a specific verb and resource: 'Find train connections between two Swiss stations.' It clearly differentiates from siblings by noting it returns trip IDs for downstream pricing/details/ticket calls, positioning it as the entry point for connection searches.

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?

Provides clear usage context: accepts station names or UIC IDs directly, so no prior station lookup is needed. Mentions that trip IDs feed downstream calls, implying a workflow, but does not explicitly name alternatives or exclusions like 'use search_stations for station lookup.'

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