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

Annotations already declare readOnlyHint, idempotentHint, openWorldHint and destructiveHint=false, so the safety profile is covered. The description goes beyond that by disclosing match semantics (matching by a word, i.e. partial/substring matching) and that results come with station codes, which helps the agent interpret output without an output schema.

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, front-loaded elements: purpose, when-to-use, and a usage example. No filler sentences; the scoping parenthetical is the only elaboration and it earns its place by disambiguating coverage.

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?

For a single-parameter lookup with no output schema, the description adequately covers what is searched, what is returned (stations with codes), and when to use it. It leaves minor gaps like result caps or behavior when no match is found, but nothing that would cause an incorrect invocation.

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 query parameter is already documented as 'Part of the station name'. The description adds a concrete example ({"query":"Dublin"}) that clarifies the expected granularity, but no additional format or matching rules beyond that, so the baseline 3 applies.

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 (Finds) plus resource (Irish Rail stations) and scopes it geographically (Republic of Ireland and Northern Ireland lines served by Irish Rail). It also notes the return content (codes), which cleanly separates it from the sibling departure/connection tools without needing to name them.

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 explicit 'Use when: a station name is ambiguous or misspelled' gives a clear triggering condition for this lookup/resolution tool. It stops short of 5 because it names no alternatives or when-not conditions (e.g. using exact station codes directly), though the trigger is unambiguous.

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