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

Annotations already declare readOnly, idempotent, openWorld and non-destructive, so safety is covered. The description adds genuinely non-redundant behavior: it enumerates the rule dimensions returned and explicitly states that unverifiable countries yield an empty result instead of a guess, which prevents the agent from treating a null as a failure.

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 tightly written sentences, front-loaded with the resource and scope, followed by the one behavioral caveat that matters. No filler or restatement of the title.

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 no output schema, the description usefully sketches the return content (days allowed, per-entry vs per-window, carnet, green card) and the empty-result case, so the agent knows what to expect. It stops short of describing response structure or units, but nothing essential for correct invocation 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% and the single 'country' parameter is fully documented in the schema (ISO alpha-2, slug, or zone code with examples). The description adds no parameter-level detail beyond that, so the baseline 3 applies.

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 resource ('temporary admission rules for a foreign-plated vehicle in one country') and enumerates the concrete fields it covers: allowed days, per entry or per window, carnet requirement, green card. This clearly separates it from visa-focused siblings such as check_visa_rules and get_route_visa_rules.

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 second sentence gives useful context that an empty result means 'no rule we can stand behind' rather than an error, which implicitly tells the agent how to interpret output. However, there is no explicit when-to-use guidance or routing to alternatives (e.g. visa rules vs. vehicle rules) despite a crowded sibling set.

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