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

Annotations already cover readOnly, idempotent, openWorld, and non-destructive, so the safety profile is set. The description adds real behavioral value by disclosing cost/rate-limit behavior ('Free within the daily allowance, then $0.002 USDC per call via x402'), which the annotations do not convey, plus the breadth of returned measures including controls with document codes.

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?

Front-loads the returned payload, then the optional parameter's effect, then the pricing model in three compact sentences with no filler. Slightly dense but every clause carries information an agent needs.

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?

Given an output schema already documents return structure and annotations carry the safety profile, the description supplies the remaining essentials: scope of measures, origin filtering, and cost. Error and pagination behavior are untouched, but for this lookup-shaped tool the coverage is sufficient.

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 both parameters are documented at baseline. The description restates the country filter's effect ('keep only what applies to that origin'), largely repeating the schema's 'filters measures to those that apply' without adding format, padding, or default details beyond the code example already in 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 resource ('One commodity code') and enumerates exactly what is returned: description, section/chapter/heading, third-country duty, and every import/export measure. This is far more informative than the title. It does not explicitly name the sibling it differs from (heading, search), but 'one commodity code' implies a single-code detail lookup.

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 only usage guidance is the origin-filtering hint ('Give country to keep only what applies to that origin'). There is no explicit when-to-use vs alternatives such as uk-trade-tariff__heading (broader level) or uk-trade-tariff__search (code discovery), leaving the agent to infer which tariff tool fits which lookup granularity.

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