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

Beyond the readOnly/openWorld annotations, it discloses cost mechanics (no charge for failed calls), a hard result cap of 25 lines, the blank-rate-on-statistical-line convention pointing to the parent heading, and the separated Chapter 99 treatment. This is genuinely useful behavioral context an agent could not get from the annotations.

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?

Purpose and the two lookup modes are front-loaded, and each subsequent sentence carries distinct information (Chapter 99, blank rates, cap, pricing). Dense but not padded; the pricing detail is slightly tangential to invocation but still relevant to calling the tool.

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?

An output schema exists so return values need no explanation, and the description covers the remaining operational gaps — result cap, empty-rate semantics, Chapter 99 separation and payment model. An agent has everything needed to call it correctly.

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%, so hts, q and limit are already documented with examples and defaults. The description reinforces the same details but adds no new syntax or format guidance beyond the schema — 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 and resource — US HTS lines fetched from the USITC HTS REST API — and enumerates the returned fields (HTS number, description, general/special/column 2 rates, units, footnotes). The 'US HTS' framing cleanly separates it from the tariff_uk sibling.

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?

Clearly explains the two lookup modes (hts number/prefix vs q search words, with the every-word-must-appear rule) and notes Chapter 99 lines come back separately. It stops short of explicitly naming tariff_uk as the alternative for non-US lookups, but the context for choosing a mode is unambiguous.

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