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

Annotations already declare readOnlyHint=true and destructiveHint=false, so safety is covered. The description adds a genuinely useful behavioral guarantee beyond that: it uses 'the same arithmetic as the site's import duty calculator,' telling the agent results are authoritative and reproducible. It stops short of disclosure on defaults or rounding, so not a 5.

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?

One sentence, front-loaded with the usage trigger before the enumeration of outputs, and every clause carries information. It is slightly run-on with the trailing calculator-comparison clause, but there is no filler.

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 correctly enumerates what is returned (customs value, duty, VAT, total), which is the key missing structured information. It does not cover default handling or the localized output of names/links, but for a read-only estimator the essential context is present.

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%, with locales and VAT rates already enumerated and documented inline, so the baseline is 3. The description adds only that duty comes from the commodity code, which the schema already conveys; it contributes no new parameter semantics (e.g. whether freight includes insurance or how defaults interact).

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 (estimates) and the exact outputs produced (customs value, UK import duty, import VAT, total), scoped to China-to-UK imports. This clearly separates it from siblings like find_duty_rate (which supplies a rate) and check_anti_dumping.

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 an explicit trigger: 'Use when the user asks how much duty and VAT they will pay to import goods from China to the UK.' It does not, however, name the complementary siblings (e.g. find_duty_rate for the commodity rate) or state when-not to use it, so a full 5 isn't earned.

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