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

Annotations already declare readOnly, idempotent, openWorld and non-destructive, so the safety profile is covered. The description adds value by naming the RDAP source and the fields returned, but omits behavior for unregistered domains, unsupported TLDs, or rate limits.

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 front-loaded sentence with zero filler; the parenthetical gloss on RDAP and the field list both earn their place.

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 rich annotations and no output schema, listing the returned fields is the right level of detail. Only minor gaps remain around failure modes such as unregistered domains or TLDs without RDAP support.

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 0% for the single 'domain' parameter, but the description's 'for any domain' clarifies that the input is a domain name rather than a URL or IP. That is modest added meaning over the bare string schema.

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 ('RDAP (modern WHOIS) lookup for any domain') and enumerates the returned data (registrar, dates, status codes, nameservers, DNSSEC). This clearly separates it from siblings like get_dns or search_domains, though no sibling is named explicitly.

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?

Usage is implied: look up registration metadata for a domain. There is no explicit when-to-use/when-not guidance, no mention of alternatives (e.g. get_dns for records, search_domains for availability), and no prerequisites stated.

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