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

No annotations are provided, so the description carries the full disclosure burden. It never mentions rate limits, RDAP throttling, per-TLD failures, or what registration fields are returned — all of which materially affect a WHOIS call.

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 tight phrase with the distinguishing protocol detail in parentheses. Nothing is padded, though the extreme brevity comes at the cost of the missing guidance noted elsewhere.

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 tool with no annotations and no output schema, the description leaves the input format, returned data shape (registrar, dates, nameservers), and failure modes entirely undocumented. It is not sufficient for confident, correct 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?

Schema description coverage is 0% — the single 'domain' parameter has an empty description — and the tool description adds no format guidance (bare domain vs. URL, IDN/punycode handling). With low coverage the description is expected to compensate and does not.

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 action and resource — 'Domain registration lookup' with the parenthetical 'WHOIS via RDAP' naming the protocol. The word 'registration' implicitly separates it from dns_lookup and subdomains, though it never names those siblings 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?

There is no guidance on when to choose this over dns_lookup, subdomains, or ip. The usage is only inferable from the tool name; no prerequisites, exclusions, or alternative-routing advice is given.

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