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

Annotations already declare readOnlyHint=true and openWorldHint=true, so the safety profile is covered externally. The description adds value by disclosing the returned data categories, but omits well-known WHOIS behaviors: rate limiting, privacy-redacted fields, and the no-record case for unregistered or restricted TLDs — all of which materially affect result interpretation.

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?

One sentence, front-loaded with the resource and immediately followed by the concrete payload contents. Nothing superfluous and nothing buried.

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 substitutes for one by listing the fields returned, and annotations cover the safety profile. It falls short only on expected edge behaviors (no record found, redacted data, rate limits), which are the main open questions for an open-world lookup.

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 coverage is 100% with a single required 'domain' parameter documented with an example, so the description need not explain it. The description adds no syntax guidance (e.g. whether a scheme, subdomain, or IDN is acceptable), leaving baseline 3 appropriate.

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 resource (WHOIS registration data) and enumerates the concrete fields returned: registrar, creation/expiry dates, name servers. It doesn't name or distinguish itself from the domain-shaped siblings like dns_lookup and ssl_check, but the resource noun ('WHOIS registration data') is distinctive enough for an agent to identify it.

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 rather than stated: an agent infers 'use this to get domain registration/ownership info.' There is no explicit when-to-use, no exclusion, and no routing advice versus dns_lookup or ssl_check, which also take a domain — a plausible confusion point left unaddressed.

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