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

Annotations declare readOnlyHint=true and openWorldHint=false, so the safety profile is already covered. The description adds one piece of genuinely useful behavior: the result is an estimate that carries its source and page URL, which matters because there is no output schema. It does not disclose how multiple receipt amounts are aggregated or what the estimate is denominated in.

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?

Short and front-loaded, with the purpose in the first phrase. However, the citation block (sources, site URL, checked October 2026) occupies more space than the functional content, and the 'same code as' URL is provenance trivia rather than decision-relevant information.

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 does carry some return-value burden and does say the estimate comes with a source and page URL. But it leaves the interpretation of stay_days and the multi-receipt aggregation behavior unexplained, which an agent needs to call this correctly.

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 67%, and the description contributes no parameter information at all. stay_days has no schema description and is never explained in prose, and nothing clarifies whether the returned estimate is per-receipt or summed across the amounts array. The description does not compensate for the coverage 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+resource: estimating a Korea tourist VAT refund. It is clearly distinguishable from the sibling calculators (electricity, taxi, GPA, loans) by domain and currency. It does not explicitly differentiate itself from any one sibling, but the domain is narrow enough that selection is unambiguous.

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?

No when-to-use, when-not-to-use, or alternative-tool guidance is given. The only contextual hint is the reference URL and citation trail, which says nothing about when an agent should call this versus, say, travel_budget. Usage must be inferred entirely from the name and title.

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