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

Annotations already declare readOnlyHint, idempotentHint, destructiveHint=false and openWorldHint=false, so the safety profile is covered. The description adds modestly useful context beyond that — that distances and drive times are approximate and that 'only areas actually served are listed' — but says nothing about freshness, pagination, or how locale affects the payload.

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?

The verb and subject are front-loaded before the long parenthetical destination list, which is dense but genuinely aids matching against user requests. The trailing sentence about only-served areas earns its place as a data-completeness caveat, though the enumeration could be trimmed.

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 zero-required-parameter, read-only lookup with no output schema, the description adequately conveys the scope and shape of the return value (facts, approximate distance, drive time, page link). Only the when-to-call-it guidance is thin.

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?

There is a single optional parameter whose schema description coverage is 100% and which already enumerates the accepted locale values and the default. The description never mentions locale or its effect on returned names, so it adds no meaning beyond the schema; 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?

The description gives a specific verb and resource ('Returns the areas served from Tokyo') and enumerates the actual content, so an agent knows exactly what data comes back. It does not explicitly contrast itself with siblings, but the sibling set (quote requests, price estimates, bus options) is functionally distinct enough that confusion is unlikely.

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 is only implied: the tool is a discovery/catalog lookup an agent would call to learn which destinations are available. There is no explicit when-to-use statement, no mention of when to prefer list_charter_bus_options or estimate_charter_bus_price instead, and no stated preconditions.

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