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

No annotations are provided, so the description carries the full burden. It helpfully enumerates the returned fields (id, name, country, coordinates, lines), which matters because there is no output schema, but it omits pagination, result limits, ordering, and what an unfiltered call returns given zero required parameters.

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 sentences, zero filler, with the purpose front-loaded and the return contract following immediately. Every clause earns its place.

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 description compensates for the absent output schema by listing return fields, which is valuable. However, with no annotations and no required parameters, an agent still cannot tell how an empty-argument call behaves or how the results are bounded, leaving a real gap for a search 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 50%: `country` is documented as ISO 3166-1 alpha-2 with an example, while `query` has no schema description. The description partially compensates by tying `query` to name matching, but adds no format details (partial match, case sensitivity, minimum length) 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 verb ('Find') and resource ('night train stations') plus the two filter dimensions, so the agent knows this is the discovery/search entry point. It contrasts naturally with get_station, but never names that sibling explicitly, so it stops short of a 5.

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?

'by name and/or ISO country code' implies when the tool applies, and the 'and/or' hints that filters combine or are optional. There is no explicit when-not guidance, no mention of get_station as the alternative when an id is already known, and no statement about behavior when both filters are omitted.

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