whois

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. It usefully discloses the payment requirement ('costs 0.4 USDC on Base via x402'), which an agent must know before calling, but says nothing about idempotency, duplicate-charge behavior, or rate limits. The mutation-guard parameter confirmNewPurchase is only explained in the schema, not in the description.

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 that lists the payload and ends with the cost note; every clause earns its place. It is dense but not padded.

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?

With no output schema, the description compensates by naming the return fields. It also covers the payment mechanism. The only shortfall is that the duplicate-purchase guard behavior is left entirely to the schema rather than being surfaced in prose.

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 100%, so both parameters are already documented in the schema, including the domain aliases and the confirmNewPurchase semantics. The description adds no parameter-level meaning beyond that, so the baseline 3 applies.

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 record for one domain') and enumerates the returned data (registration/expiry dates, registrar, status codes plus SEO metrics), so an agent knows exactly what it retrieves. It does not explicitly differentiate itself from nearby siblings like domain_tech, domain_rank, or domain_security_check, which keeps it from a 5.

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 when-to-use guidance, no statement of when this is preferable to domain_tech or domain_security_check, and no prerequisites. The only contextual signal is the cost, which is pricing rather than usage direction.

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