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

Annotations already cover read-only/idempotent/open-world safety, and the description adds genuinely non-obvious behavior: which duty programs are included (Section 301, FTA preferential) and explicitly which are excluded (Section 232, IEEPA, AD/CVD, fees). This prevents the agent from treating the total as full landed cost. It stops short of noting accuracy caveats, origin-qualification requirements, or error behavior.

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?

A single dense sentence with no filler, and includes/excludes information is packed in efficiently. The terse 'in'/'out' shorthand is slightly harder to parse than plain prose but costs no extra length.

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?

There is no output schema, and the description does explain the return values (total and effective rate) plus the applied rate composition and exclusions. Missing only edge behavior: what happens with a missing/invalid code, when origin does not qualify for FTA, or whether unit is required for specific duties.

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?

With only 40% schema coverage, the description compensates for most undocumented params: value as USD customs value, origin as the qualifying country driving FTA/301 treatment, and quantity implied by 'specific with quantity' duties. The 'unit' parameter is never addressed, leaving one gap.

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 ('Duty estimate for one HTS code') and scopes it to a single code, which distinguishes it from lookup_hts_code/search_hts that only resolve codes. It also enumerates the components of the result (ad valorem, specific, Section 301, FTA, total, effective rate), so the agent knows exactly what it gets.

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 phrase 'for one HTS code' implies you must already have a code (i.e. call lookup_hts_code/search_hts first), but there is no explicit when-to-use, when-not-to-use, or sibling routing. Usage is inferable rather than stated.

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