Visa requirement for one passport + destination pair: category, fee, processing time, max stay, validity, documents, official source, last verified date, and the stay-extension rule. Always pass both arguments.
| Name | Required | Description | Default |
|---|---|---|---|
| lang | No | Page language for the returned URL, default en | |
| passport | Yes | Passport ISO-3166-1 alpha-2, e.g. fr | |
| destination | Yes | Destination slug, e.g. japan |
Changes observed during successful MCP inspections.
Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
With no annotations, the description carries the full burden. It discloses the returned data fields well, which is helpful for a tool lacking an output schema, but it omits behavioral details like whether results are live or cached, rate limits, or error handling. The 'always pass both arguments' constraint is a minor behavioral note.
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 efficiently lists the return fields, and the second is a short constraint. It is front-loaded with the core purpose and avoids unnecessary verbosity, though the closing argument reminder is slightly redundant given the schema's required flags.
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 no output schema, the description usefully enumerates the return payload, which an agent would otherwise have to infer. It covers the essentials for calling the tool, though it could briefly mention the optional language parameter's effect or error behavior for full completeness.
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 the input schema already fully documents all three parameters with examples. The description adds 'Always pass both arguments,' which is redundant with the required fields, and provides no extra syntax or format guidance beyond what the schema supplies.
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 resource (visa requirement) for a passport+destination pair and enumerates the returned fields (category, fee, processing time, etc.), making the tool's scope clear. It does not explicitly differentiate from siblings like extension_rules or passport_power, but the lookup nature is distinct.
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 guidance is 'Always pass both arguments,' which addresses parameter usage rather than when to choose this tool over alternatives. No context about when to use it versus siblings such as extension_rules or list_destinations is provided.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.