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

Annotations already declare readOnlyHint/openWorldHint=false/destructiveHint=false, so safety is covered. The description adds genuinely useful behavior beyond that: airline enforcement, nationality-dependent variance, volatility ('change without notice'), and an 'information, not advice' disclaimer. Not a full 5 since it doesn't describe output shape or data freshness guarantees.

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 core purpose, then the operational stakes, then parameter behavior, then caveats. Dense but each sentence carries information; only the parenthetical examples risk slight bloat.

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 an output schema present, the description rightly focuses on scope, usage, and caveats rather than return values. It is essentially complete for a single optional-parameter lookup tool; the only gap is not positioning itself explicitly against sibling eligibility/visa tools.

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%, so the baseline is 3, but the description adds real semantics the schema does not: passing cc scopes to one destination and omitting it returns all destinations. That optionality behavior is not evident from the schema alone.

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 ('entry requirements for a destination') and enumerates the two rule families it returns: passport-validity rules (6-month rule, Schengen 10-year issuance cap, blank pages) and health/vaccination rules. This clearly separates it from siblings like check_visa_requirement, check_visa_free, and get_passport_renewal.

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?

Gives clear operational context ('a valid-looking passport is refused BOARDING if it fails these') and parameter usage ('Pass cc for one destination; omit for all'), so the agent knows when the tool matters. It stops short of explicitly naming which sibling to use instead (e.g., check_visa_requirement), so it is clear context without exclusions.

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