Domain WHOIS/RDAP

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

Annotations already declare readOnlyHint, openWorldHint, idempotentHint, and destructiveHint=false, so the agent knows this is a safe read. The description adds useful context by listing the specific WHOIS/RDAP fields returned and by noting that the data is analytics-only. However, the 'not clearance' phrase is ambiguous and could use clarification about intended vs. disallowed use cases.

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?

The description is compact and front-loaded: it identifies the endpoint, the action, the returned fields, the recommended sequence, and a caveat — all in two sentences. Every clause earns its place without unnecessary elaboration.

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?

For a single-parameter, read-only tool with rich annotations and a 100% schema coverage, the description is largely complete: it states what is returned, when to call it, and a usage caveat. The absence of an output schema is mitigated by the explicit field list. Minor gaps remain around error conditions and the exact meaning of 'not clearance,' but these do not prevent correct selection and invocation.

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?

The input schema already covers the single 'domain' parameter with a clear description and example. The tool description reinforces that the parameter is a domain name via the WHOIS/RDAP context, but adds no new parameter-level meaning beyond the schema's 100% coverage.

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 states a concrete action ('look up'), the specific resource ('domain WHOIS/RDAP'), and enumerates the returned signals (registration, registrar, age_days, status, nameservers). This clearly differentiates it from sibling tools like domain.dns and domain.tls, even though a plain 'whois' sibling exists.

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 gives explicit guidance on when to call it: 'Call after url.open when you need registration age / registrar signals.' It also adds a limitation: 'Analytics-only — not clearance,' which helps an agent decide whether this tool is appropriate. It does not explicitly name excluded alternatives, but the use-case framing is sufficiently clear.

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