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

Annotations already cover the read-only, idempotent, non-destructive profile, so the bar is lower, yet the description adds real behavioral nuance: the Cyprus conditional 60-day rule is flagged only when you're not 183+ resident elsewhere, ratings are safe/warning/triggered, and it frames the output as early-warning day math rather than tax advice. It does not discuss pagination or limits, but for a computation tool that is minor.

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 comprehensive engine' and organized into three numbered output groups, so the structure is clear. It is dense to the point of reading as one long passage, but nearly every clause carries useful information.

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 an output schema and rich annotations already present, the description completes the picture by stating scope (single itinerary input), the caveat (not tax advice), and the sibling supersession. Nothing an agent needs to invoke it 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 coverage is 67% and the description only elaborates on the optional income parameter ('enables the tax-cost projection for at-risk countries'). The stays structure and referenceDate are documented by the schema itself, so the description adds marginal meaning beyond structured fields. Baseline 3 is appropriate here.

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 engine and enumerates exactly the three outputs it produces (Schengen 90/180 status, per-country tax-residency risk, optional tax-cost projection). It explicitly distinguishes itself from check_schengen / check_residency / check_tax_residency_risk by declaring it supersedes them, so an agent can disambiguate without opening the schema.

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?

It clearly frames this as the comprehensive replacement for three named sibling tools (all still available), which gives strong routing context. It stops short of saying when the narrower siblings are still the better choice, so a full 5 is not warranted.

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