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

Annotations already cover the safety profile (readOnly, non-destructive, closed-world), so the description earns credit for adding provenance and caveats the annotations cannot convey: the Passport Index dataset as source, corroboration and IATA verification links returned with the answer, and that entry rules change without notice with the destination authority final. It does not mention caching, rate limits, or how stale the data can be.

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?

The first sentence front-loads the core concept and enumerates outcomes compactly; the second sentence carries data coverage and provenance; the third is a short disclaimer. It is slightly dense with parenthetical asides, but every clause serves a purpose and there is no padding.

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 lookup with a full output schema, the description supplies what the schema cannot: outcome taxonomy, dataset breadth, provenance, and a legal-accuracy caveat. It even notes the corroboration and IATA links returned, so the agent knows extra verification data comes back. The only gap is alternative-tool routing, which is marginal for such a simple point lookup.

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 the schema already documents both parameters well, including the tricky 'Schengen (checked via Germany)' case. The description adds only the one-per-call scoping ('ONE nationality', 'ONE destination') and no additional format or syntax meaning, so the baseline of 3 applies.

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 with exact scope: 'VISA REQUIREMENT for ONE nationality travelling to ONE destination', then enumerates every outcome class it can return (visa-free, visa on arrival, e-visa, ETA, visa required, no admission). This implicitly separates it from siblings like check_visa_free (visa-free only) and list_visa_free_destinations (many destinations for one passport), so an agent can route without opening any schema.

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 'ONE nationality / ONE destination' framing and the '199 passports x 199 destinations' coverage tell the agent clearly when this lookup is the right call, and the disclaimer sets expectations about authority. However, it never names an alternative or an exclusion (e.g. when to prefer get_entry_requirements or check_visa_free), leaving that routing to inference.

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