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

With annotations covering the safety profile (readOnly, idempotent, non-destructive), the description adds substantial extra context: it discloses data sources and what is deliberately excluded ('never registrant contacts'), describes the risk-flag output, and details billing behavior ('Costs $0.005 USDC per successful call (x402, eip155:8453); failures are not charged'). This is exactly the cost/failure semantic an agent needs to decide whether to invoke.

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 purpose and scope are front-loaded, followed by data sources, an important scope caveat, and pricing. It is dense and somewhat packed into long parenthetical clauses, but nearly every detail (excluded registrant contacts, failure billing, cost) earns its place for agent decision-making.

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, so the description carries the burden of describing returns — and it does, listing each signal category (DNS, RDAP fields, TLS validity/issuer/expiry, final URL/status/HSTS) plus risk flags. Combined with the billing and 'does not exist' caveats, an agent has everything needed to call and interpret it.

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?

There is a single parameter with 100% schema coverage including a pattern and example, so the schema already carries the semantics. The description adds only the framing 'Given a domain' and no format or edge-case guidance (e.g., IDN handling, subdomains) beyond what the schema provides; 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 verb (verify) and resource (domain), then enumerates the exact evidence gathered — DNS records, RDAP registration data, TLS certificate, website response, and risk flags. This level of specificity lets an agent distinguish it from siblings like site_audit, sec_company, or company_card without opening the schema.

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 description implies its use case (checking whether a domain is a real, live business) and clarifies that 'does not exist' is a valid outcome, but it never names an alternative tool or states when a sibling such as site_audit or sec_company would be preferable. Usage is inferable but not routed.

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