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

Beyond the annotations (readOnly, idempotent, openWorld, non-destructive), the description discloses pricing ($0.01 USDC via x402 on Base), no-charge failure modes (data source down, invalid input), and the payment-required response when unpaid. These are exactly the auth/cost behaviors an agent needs before invoking.

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 sentences, front-loaded with what the tool does and followed by commercial/failure terms. Dense but every clause carries operational value; the enumerations are long but necessary for scope.

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?

No output schema exists, and the description carries most of that burden by naming the score range, verdict levels, and reason codes, plus pricing and error semantics. Only gap is that the reason codes themselves are not illustrated or enumerated.

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 the schema description fully documents it (accepts domain, email, or URL and normalizes to domain). The description adds no parameter-level detail beyond the schema, so the 100%-coverage baseline of 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 verb ('vetting/scoring') and resource (domain) and enumerates exactly what is combined (RDAP age/status, DNS, MX, SPF, DMARC, DKIM, HTTPS probe) into named outputs (0-100 score, verdict, reason codes). The phrase 'one-call' distinguishes it from single-source siblings such as domain_rdap_lookup or email_auth_check.

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?

'One-call domain vetting' implies this is the aggregate alternative to calling individual lookups, and the cost/payment clauses tell the agent what to expect. There is no explicit 'use this instead of X when Y' routing statement, but the context is clear enough to select correctly.

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