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

Annotations already declare readOnlyHint=true, idempotentHint=true, destructiveHint=false and openWorldHint=true, so the safety profile is covered. The description adds real behavioral context: each rule ships with a verbatim official quote and source link, and a country without data returns an error rather than an empty result. That error semantics disclosure is the kind of thing annotations cannot express.

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-loaded with the core purpose and the most decision-relevant detail (error behavior) before the usage sentence. The content list is repeated twice (once as 'food bans, cash declaration, alcohol and tobacco limits…' and again as 'alcohol, tobacco, cash, meat and other food, goods limits'), which is mild redundancy rather than 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?

An output schema exists, so the description need not explain return structure; it still usefully notes the quote/source-link payload and the error-on-missing-data behavior. With 100% parameter coverage and full annotations, the agent has everything needed to call it correctly, leaving little beyond a sibling comparison unaddressed.

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 country_code, from and locale are fully documented in the schema. The description adds only the implicit point that the 'from' country is optional and origin-sensitive; it contributes no syntax or format beyond what the schema already provides. Baseline 3 is correct.

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 and resource ('Customs rules when driving into a country') and enumerates the covered domains (food bans, cash declaration, alcohol/tobacco limits, goods value, fuel canister). It does not explicitly name a sibling such as get_vehicle_import_rules, so the boundary is left implicit, but the purpose is unmistakable.

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?

'Use it for what you may bring in by car: alcohol, tobacco, cash, meat and other food, goods limits' gives clear positive context, and the error-case warning ('never present that as nothing is restricted') is genuinely useful guidance. There is no explicit when-not-to-use or named alternative, so it stops short of a 5.

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