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

Annotations already cover the safety profile (readOnly, idempotent, openWorld, non-destructive), yet the description adds real behavioral detail beyond them: the returned fields (rate, basis, sources, date), the non-percentage-rate-as-text failure mode, the EU duty lookup gap, and the exclusion of US chapter 99 additional duties.

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?

Dense but front-loaded: purpose first, then inputs, then return shape, then caveats. Every sentence carries information, though the caveat cluster (EU duty, text-only rates, chapter 99) packs a lot into a short span.

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 six-parameter estimation tool with an output schema, this covers the essentials an agent needs: required inputs, currency constraint, EU VAT member-state handling, return shape, and the known data gaps that could otherwise cause silent misinterpretation of results.

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 83%, so most parameters are already documented. The description still adds meaning: hs_code is 'a candidate, not binding,' all amounts must share one currency with no conversion done, and 'country' supplies the EU member-state VAT rate. These clarify intent rather than restating the schema.

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 ('estimate duty, VAT and total landed cost') and pins the scope to UK/US/EU shipments from a tariff line. It also implicitly differentiates from the eu_duty_estimate sibling by stating 'EU duty is not looked up.'

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?

Gives a clear trigger phrase ('what will import duty and VAT be on this?') and a usable when-to-use context. It does not explicitly route an agent to the sibling eu_duty_estimate when full EU duty data is wanted, and the 'destination can be EU but EU duty is not looked up' nuance is left for the agent to reconcile.

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