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

Annotations already declare this as a read-only, idempotent, non-destructive, closed-world operation, and the description earns credit beyond that: it discloses the 6-passenger cap and hire-car licence conditions for the Alphard, the rule that add-on cars require a coach booking, and the exact scope of the fixed_prices (JPY, tax included, 2 h in Tokyo, airport transfers, day trips). It stops short of covering availability, seasonality, or what "verification status" means operationally.

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 purpose is front-loaded, but the body is a single dense run-on paragraph with stacked parentheticals (licence terms, regional scope, pricing scope) that makes it harder to scan than a short bulleted breakdown. Most sentences carry real information, but the packaging is heavier than necessary.

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 carries the return-value burden and does so reasonably, naming passenger seats, auxiliary seats, luggage information, verification status, and the fixed_prices block. It is nearly complete for a zero-required-parameter catalogue call; the remaining gaps are the meaning of verification status and whether the catalogue can be empty.

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 the baseline is 3; the description adds meaning by tying the passenger and suitcase counts together into a "recommended combination" use case, and by clarifying that returned seat counts exclude the driver and that auxiliary (fold-down) seats can be excluded from counts. This goes beyond restating the schema field descriptions.

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 uses a specific verb-plus-resource ("Lists bus and coach types available for chartered group transport") and enumerates the exact catalogue contents: charter coaches, minibuses, the 7-seat Alphard, and add-on cars. It does not explicitly route the reader away from the sibling estimate_charter_bus_price, even though it also returns prices, so the boundary between the two is left to inference.

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 rather than stated: the passengers/carry_on_bags/large_suitcases parameters are flagged as triggering an optional recommendation, and "quote these exactly" is an instruction on handling the returned fixed_prices. There is no explicit when-to-use/when-not guidance and no mention of when to prefer create_quote_request or estimate_charter_bus_price instead.

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