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

Annotations only cover read-only and closed-world semantics; the description adds substantially more: per-call cost (1 prepaid credit), the exact 402 payment_required failure mode with buy links, a 'not legal advice' caveat, and a dataset freshness date. This is the kind of operational context 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?

Dense single paragraph that front-loads the trigger, then inputs, then outputs, then cost — a sensible priority order. Slightly overpacked, with the input example duplicating the schema and the source-link inventory bordering on excess, but every clause carries real 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?

There is no output schema, and the description compensates by naming the return fields (visa_free_for_ordinary_passports, max_days) and the route taxonomy with conditions, validity windows and sources. Combined with the cost and failure-mode disclosure, an agent has everything needed to call and interpret it.

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 parameter is already documented there, so the description's 'English country name, e.g. Germany' adds no new syntax or format detail. Per the rubric, a fully covered single-param schema defaults to baseline 3.

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 ('whether a passport holder can enter mainland China without a visa') and even scopes the answer to duration. The 'mainland China' qualifier cleanly separates it from any sibling that might cover other regions, and the output summary makes the tool's contract unambiguous.

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?

Opens with an explicit trigger ('Use when someone asks whether...'), which is exactly the when-to-use guidance an agent needs. It also routes the agent to get_pricing for the credit-purchase path. It stops short of stating when NOT to use it (e.g., Hong Kong/Macau/Taiwan, or non-ordinary passports), which is the only reason it isn't a 5.

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