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

Annotations already declare readOnlyHint, idempotentHint, openWorldHint and destructiveHint=false, so the safety profile is covered. The description adds the batch limits (up to 10 passports) and hints at a 'tightest leg' aggregate in the response, which is modest extra context but no auth, rate-limit, or failure-mode detail.

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?

A single sentence with the route-scoping benefit front-loaded and no filler. It is dense but readable; the closing 'plus the tightest leg of the route' clause is informative though slightly compressed.

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 return values need not be explained, and the 100%-covered input schema handles parameters. The description covers what the tool does for a 4-param, one-required read tool; only cross-tool routing guidance is thin.

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 locale, weight, countries and passports are all already documented with semantics and enums. The description restates the passport limit (10) but adds no format or meaning beyond the schema; 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+resource (visa rules) scoped to a route, plus the batch capability (up to 10 passports) and the distinguishing 'tightest leg' output. It differentiates itself from siblings like check_visa_rules by implication of route-wide batching, but never names the alternative explicitly.

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 framing ('in one call', multi-country, multi-passport), which suggests this is the batch/route variant, but there is no explicit when-to-use vs. check_visa_rules guidance or exclusion criteria. An agent must infer the routing from the phrasing alone.

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