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

Annotations already declare readOnlyHint=true and destructiveHint=false, so the safety profile is covered. The description adds valuable behavioral context: the Schengen 10-year issuance cap invalidates passports whose printed expiry is still in the future, and rules vary by nationality and change without notice. It also discloses the 'Information, not advice' limitation. This goes beyond the annotations without contradicting them.

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 description is dense but well-organized: it front-loads the core purpose, then details the specific rules, then gives the operational warning and usage instruction. Every sentence earns its place. It's slightly long but the density of useful information justifies the length.

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 read-only lookup tool with one optional parameter and an output schema, the description is nearly complete. It covers what the tool returns (entry requirements), how to invoke it (cc optional), and important caveats (enforcement varies, changes without notice). The only minor gap is not describing the output schema's structure, but the output schema exists and the description needn't explain return values per the rubric.

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% for the single 'cc' parameter, so the schema already documents it. The description adds meaning by explaining the parameter's role ('Pass cc for one destination; omit for all') and its semantics (ISO alpha-2 destination country code is in the schema, but the description clarifies the omission behavior). This is a meaningful addition beyond the schema.

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 ('get') and resource ('entry requirements') with a clear scope: passport-validity rules and health/vaccination entry rules for a destination. It distinguishes itself from siblings like check_visa_requirement and get_document_checklist by naming the specific rule types (6-month rule, Schengen 10-year cap, blank pages, yellow-fever certificate).

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 description explicitly says 'Pass cc for one destination; omit for all' — a clear usage instruction. It also provides operational context ('a valid-looking passport is refused BOARDING if it fails these') that tells the agent when this tool matters. While it doesn't name sibling alternatives, the specificity of the rule types makes the use case unambiguous.

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