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

Goes well beyond the readOnlyHint/openWorldHint annotations: discloses the exact data source (English chapter page only), schedule vintage (2026-04-01), encoding (Shift_JIS decode), and the payment model ($0.002 USDC via x402 on Base/Solana/Arc, failed calls free). Cost and payment/auth requirements are precisely what an agent needs before invoking a paid tool.

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 sentences, purpose front-loaded, then source constraints, then pricing. Every sentence carries information; the pricing sentence is long but justifies its length since cost is decisive for a paid call.

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 an output schema covering return shape and annotations covering read-only safety, the description need only add source, vintage, encoding, and cost — all present. Minor gap: no note on coverage limits (which chapters/headings exist) or behavior when the HS code is not found.

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 description coverage is 100% and the single `hs` parameter is already documented with 4-digit/6-digit, dot-optional semantics and examples. The description's inline examples restate what the schema provides rather than adding new constraint detail, so 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+resource: Japan Customs import tariff lines for an HS heading/subheading, with concrete input examples (8703, 8703.21). The Japan/HS-tariff specificity inherently separates it from logistics_china_customs_tariffs, logistics_uk_trade_tariff and energy_world_customs_tariff_wits, though no sibling is named 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?

Usage is implied by the resource scope (look up a tariff line by HS code), but there is no explicit when-to-use or when-not guidance, and no pointer to alternatives such as the HS classifier or duty calculator. An agent must infer the routing itself.

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