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

Annotations already cover the safety profile (readOnlyHint=true, destructiveHint=false, idempotentHint=true, openWorldHint=false), so the bar is lower. The description still adds real context beyond them: the data source and its parity with the public page, the ranking basis (relevance), and the empty-result behavior on low confidence, which an agent could not infer from 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?

A single dense paragraph that front-loads the core purpose before moving to result shape and input guidance; every sentence carries information. Minor redundancy in restating the 5-candidate cap that the schema and output schema already define.

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 two-parameter, read-only tool with 100% schema coverage, an output schema, and full annotations, this is close to sufficient: source, ranking, per-candidate fields, and empty-result semantics are all present. The remaining gap is the missing routing rule against the sibling tariff lookup tool.

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 100% and both parameters already document their own constraints (limit range 1-5 with default 5, product_name maxLength 200 with a specificity example). The description largely repeats this ('up to 5 most relevant candidates', 'the more specific the better') rather than adding syntax or format detail. Baseline 3 for a schema that does the heavy lifting.

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?

The description states a specific verb and resource: look up Taiwan CCC tariff code candidates from a product name/description, via the same search engine as the official query page, drawing on 12,000+ Customs Administration records. That is far more concrete than a tautology. It stops short of naming the sibling it is not (lucky_ccc_tariff_lookup appears to be the by-code counterpart), so an agent must infer the split itself.

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?

It does give input guidance that affects results ('the more specific the description — brand/model/material/use — the higher the accuracy') and states that an empty result is returned when no high-confidence candidate exists. But it never says when to choose this tool over lucky_ccc_tariff_lookup or the broader lucky_ccc_tariff_lookup-style siblings, so usage is implied rather than routed.

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