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

Annotations already declare readOnly, idempotent, non-destructive, and open-world, so the safety profile is covered. The description adds behavior beyond that: the accepted input forms (name or code) and a grounding rule forbidding supplementation from memory, plus an unofficial/not-affiliated disclaimer. It stops short of describing lookup failure or ambiguity handling.

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?

Front-loaded with the returned fields, then the input formats, then the grounding constraint and disclaimer. Each sentence does work, though the disclaimer is somewhat boilerplate and could be compressed.

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?

An output schema exists, so return structure need not be explained, and the description still previews the answer categories. For a single-parameter lookup, the input formats and grounding rule are the material gaps an agent would have, and both are covered; only ambiguity/error behavior is missing.

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 0%, so the description carries the full burden for the single 'station' parameter — and it does, giving two concrete accepted formats ("Gallery Place", "B01"). It does not state matching rules (case sensitivity, partial names, ambiguous matches), which keeps it short of a 5.

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 names the concrete resource (a station) and enumerates exactly what it returns: lines served, address, parking, transfers, entrances. That is far more specific than a tautology, though it does not explicitly distinguish itself from adjacent siblings like transfers_at or get_route, which also touch station-level data.

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?

Usage is implied by the returned-field list, and the note that a station can be given as a name or a code helps selection, but there is no explicit when-to-use or when-not-to-use guidance and no pointer to alternatives such as transfers_at for transfer-specific questions or find_stops_near for proximity.

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