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

No annotations are provided, so the description carries the full behavioral burden. "Live registry lookup" is a genuine value-add: it signals a real-time network call with possible latency, rate limits, or failure modes. However, it says nothing about what happens for unregistered or invalid domains, whether results are cached, or error behavior — meaningful gaps for a live external lookup.

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, zero filler, with the core action and returned fields front-loaded ahead of the short qualifier about live lookup. Nothing is repeated and nothing could be cut without losing 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?

For a single-parameter, read-only lookup with no output schema, the description usefully enumerates the return fields, which compensates for the absent output schema. Missing only the input-format convention and any note on error/unregistered-domain behavior; otherwise complete for this complexity level.

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?

One parameter with 100% schema description coverage, so the baseline is 3. The description adds no guidance about acceptable input form — whether to pass a bare apex domain, a subdomain, an IDN, or a URL with scheme — and the schema's "Domain name" is equally silent.

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 and resource ("Return registration data for a domain") and enumerates the fields returned: registrar, creation/expiry dates, nameservers, status. The WHOIS framing makes it distinguishable from dns_lookup or ens in practice, but it never names those siblings explicitly, so the differentiation is inferential rather than stated.

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 explicit when-to-use or when-not-to-use guidance, and no mention of the closely related siblings (dns_lookup, ens, ssl_check, ip). Usage is implied by the resource — an agent seeking domain registration metadata will recognize this — but nothing routes it away from alternatives.

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