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

Annotations already declare readOnly, idempotent, openWorld and non-destructive, so the safety profile is covered. The description adds real behavioral context beyond that: it discloses the coverage caveat that an unverified country 'returns nothing rather than a guess', telling the agent that an empty result means no data rather than an error or a zero-day allowance.

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?

Two dense sentences with zero filler: the second sentence, the coverage caveat, is arguably the most decision-relevant information and is given equal weight. Nothing is repeated from the schema or annotations and nothing is padded.

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 only two well-documented parameters, rich read-only annotations, and an output schema handling return shape, the description needs to cover only purpose and surprising behavior — and it does both, including the empty-result semantics. Nothing an agent needs to invoke this correctly is missing.

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% — both 'country' and 'locale' are documented in the schema, including the locale enum and its fallback behavior. The description adds only 'in one country', which restates the single-country scoping already implied by the required country parameter. Baseline 3 is correct when the schema carries the parameter semantics.

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 names a specific resource — temporary admission rules for a foreign-plated vehicle in one country — and enumerates the exact facts returned (allowed days, per entry vs per window, carnet, green card). An agent can tell it apart from general customs or visa tools on field content. It stops short of 5 because no sibling (e.g. get_customs_rules, check_visa_rules) is explicitly contrasted.

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?

Usage is implied by the tool name and the phrase 'in one country', which makes the country-scoped lookup obvious. However, there is no explicit statement of when to use this versus get_customs_rules or check_visa_rules, and no prerequisites or exclusions are given. Adequate but with a clear routing gap.

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