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

It prominently discloses the $0.002 USDC cost, which is material behavioral context beyond the annotations, and clarifies that the data source is RDAP. The readOnlyHint=false does not contradict the description; the paid nature is a plausible reason the tool is not marked read-only, and no side effects are claimed either way.

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?

The cost warning is front-loaded, and the whole description is one tight sentence plus a useful fraud-signal parenthetical. There is no redundant or filler text.

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 usefully lists the expected return fields and covers the practical cost and fraud use case. It omits small operational details like error or quote-flow semantics, but the payment_signature schema description fills the main remaining gap.

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?

The payment_signature parameter is already well documented in the schema, but the required domain parameter has no schema description. The description only implies that a bare domain is the input, without examples or guidance about URL formats, IDNs, or punycode.

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?

The description clearly enumerates the return fields (registrar, age, expiry, status, nameservers) and identifies RDAP as the source. It does not use an explicit action verb or name sibling tools, so it is clear but not fully differentiated beyond the whois-specific name.

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?

The parenthetical 'young domains are a fraud signal' implies a fraud-assessment use case, giving some selection context. However, it does not state when to prefer this tool over related checks such as email_check, sanctions screening, or wallet_brief, nor does it mention exclusions.

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