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

Annotations already declare readOnlyHint=true, idempotentHint=true, and destructiveHint=false, so safety is covered. The description goes beyond annotations by disclosing the scope of behavior: it returns a registration-state classification and the full raw registry record, and supports 1400+ zones including IDN/Cyrillic domains. No contradictions or hidden side effects are apparent.

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 sentences with no filler. The primary action is front-loaded, followed by output details and a notable capability (1400+ zones, IDN). Every sentence contributes useful selection and invocation 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?

Given the low parameter count, complete schema coverage, robust annotations, and an output schema, the description covers what a caller needs: domain input, expected result categories, and supported zone coverage. It is not verbose, and no critical missing context stands out.

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 documented with an example and IDN guidance. The description's mention of IDN support is somewhat redundant, so it adds little beyond the schema, earning the 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?

The description uses a specific verb and resource ('Look up WHOIS/RDAP data for a domain') and lists concrete output categories (registration state, registrar, dates, name servers, status). This clearly distinguishes it from the sibling tools ip_geolocation and punycode_convert, which target different data transformations.

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 description provides clear context: use this tool when you need domain registration WHOIS/RDAP data, including IDN zones. It does not explicitly spell out 'when not to use' or name alternatives, but the domain-specific scope makes the intended use unambiguous against the siblings.

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