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

Annotations already declare readOnlyHint=true and openWorldHint=true, so the safety and external-network profile is covered. The description adds useful context by naming RDAP/WHOIS as the protocol and listing the data categories returned, but omits rate-limit behavior, whether queries are cached, and what happens on unregistered domains.

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 tightly written sentence with no filler; the verb and resource are front-loaded and the returned data categories are appended efficiently.

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 one-parameter, read-only lookup with no output schema, the description is sufficient: it names the protocol and the categories of data returned, and annotations cover the safety/open-world profile. The only meaningful gap is not clarifying its relationship to the overlapping domain_report sibling.

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% for the single 'domain' parameter, which already documents IDN support and the IP-address exclusion. The description adds no parameter-level detail beyond what the schema provides, so the baseline 3 applies.

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 (look up) and resource (domain registration data) and enumerates the returned fields (registrar, dates, statuses, nameservers) plus the protocol (RDAP/WHOIS). It does not, however, distinguish itself from adjacent siblings like domain_report or dns_query, so the 5-level sibling-differentiation requirement is unmet.

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?

There is no when-to-use or when-not-to-use statement, and no alternative tool is named. The only scoping hint (IP addresses not accepted, IDNs accepted) lives in the schema property description, not in the tool description, so it adds nothing here.

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