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

No annotations exist, so the description carries the full behavioral burden. It does disclose the shape of the result (registrar, dates, name servers, flags), which is genuinely useful, but says nothing about WHOIS rate limiting, privacy-redacted records, or what happens for unregistered/invalid domains — the failure modes an agent most needs to anticipate here.

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 tight sentences: the first front-loads what the tool returns, the second adds purpose. There is no redundant or filler wording, and the most decision-relevant information (the data fields) comes first.

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 tool with no output schema, the description is nearly complete because it names the returned fields instead of leaving the response opaque. The remaining gap is behavioral: no note on rate limits, redaction, or errors for unknown domains.

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?

Only one parameter, and schema coverage is 100% ("Domain name (no scheme)"), so the schema already carries the semantics. The description adds nothing further — no guidance on IDN, subdomains, or TLD support — which is the baseline 3 case.

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 ("WHOIS lookup for a domain") and enumerates the returned data: registrar, creation/expiry dates, name servers, status flags. That enumeration distinguishes it cleanly from the many sibling check_* tools that query live DNS/HTTP (check_dns, check_asn, check_ssl) rather than registration records.

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?

"Useful for domain age verification and expiry monitoring" implies the use case but gives no explicit when-to-use vs. alternative routing (e.g. check_dns for records, check_wayback for history of a site). The agent must infer that this is the registration-data tool from the field list alone.

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