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

With no annotations, the description carries the full load and does well: it discloses that data is static/reviewed rather than real-time, that every fact is attributed to a source, and that coverage is limited to Southern Lakes and Fiordland. It does not cover what happens when no reviewed route exists or how many facts are returned, which keeps it from a 5.

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 short sentences, front-loaded with the capability and ending on the highest-value constraint (not live data). Nothing is padded or repeated from the schema.

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 simple two-parameter lookup with no output schema, the description supplies the missing return-value context (distances, drive times, services, sourced) and the regional boundary. Only the not-found/empty-result behavior is left unstated.

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 both from/to are already documented with place examples. The description adds only that the pair represents travel between two places within a named region; it gives no format, disambiguation, or ordering guidance 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 ('List') and resource ('reviewed facts on getting between two places'), plus the concrete data types returned (distances, drive times, services). The geographic scope and the explicit 'not live road or timetable information' caveat separate it cleanly from the sibling live_conditions.

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 exclusion 'Not live road or timetable information' effectively tells the agent when to route elsewhere, and the 'reviewed facts... each with its source' framing implies planning/research use. It stops short of naming live_conditions or any alternative as the replacement, so the routing is implied rather than explicit.

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