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

Annotations already declare readOnlyHint, idempotentHint, openWorldHint and destructiveHint=false, so safety is covered. The description adds two useful behavioral facts beyond them: matching works against both Finnish and Swedish spellings, and results come back with short codes. Result limits/ordering are not mentioned, but that is a minor gap given annotation coverage.

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?

Three short lines, front-loaded with the purpose, then the trigger condition, then a concrete example. No sentence is redundant and nothing is buried.

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?

With no output schema, the description correctly discloses what comes back (matching stations plus their short codes), which is the key missing piece. It does not say whether results are ranked or capped, a small omission for a search tool that could return many matches.

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% and the schema already explains "Part of the station name", so the baseline is 3. The description adds value by clarifying that matching is word-based and language-flexible (Finnish or Swedish), and the {"query":"Helsinki"} example concretely shows a single-token query works.

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 and resource: finds Finnish passenger stations by name fragment, and notes it also surfaces the short codes used elsewhere. The station-lookup resource is clearly distinct from the sibling tools (fi_station_departures, fi_train_connections), though the description never names those siblings to draw the contrast explicitly.

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?

"Use when: a station name is ambiguous or misspelled" gives an explicit trigger condition, which is exactly the right context for a fuzzy name resolver. It does not state when not to use it (e.g., when the code is already known and a trip query can be issued directly), so it stops short of full routing guidance.

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