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

Annotations already cover read-only/non-destructive/open-world, and the description adds genuinely new behavioral facts: per-call cost of $0.01 via x402 USDC or card key, first 25 free, failed calls free, and that repeat calls are not free (clarifying the idempotentHint=false). It also restates safe behavior ('reads or computes only and changes nothing') and implies open-world dependency via RDAP/WHOIS.

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?

Front-loads the resource and its payload, then usage, then an example, then pricing/auth — a sensible order with no filler sentences. Slightly dense, with the final sentence packing cost, free-tier, failure billing, and safety into one long clause. The title/description overlap on the record list is minor redundancy.

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, no-output-schema tool this is complete: it tells the agent what data comes back (since no output schema exists to do so), what it costs, how payment works, and that the call has no side effects. The only remaining gap is sibling differentiation, which is a routing concern rather than a completeness one.

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% and there is only one parameter, so the schema already documents 'name' fully with the same example. The description's 'Example: name=cloudflare.com' merely repeats the schema example and adds no format, TLD, or normalization rules. Baseline 3 is appropriate when the schema carries the parameter semantics.

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?

Names a concrete verb/resource pair ('WHOIS and domain lookup in one call') and enumerates the returned data: registrar, registration/expiry dates and age, DNS record types (A, AAAA, CNAME, MX, NS, TXT, CAA), DNSSEC, and SPF/DMARC. That is far more specific than a restated title. The gap: it does not distinguish itself from siblings like dns_lookup, domain_report or pack_domain_intel, which clearly overlap in returned data.

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?

Gives explicit usage contexts: 'check who owns a domain, how old it is, where it is hosted or whether it accepts mail, for lead research, trust and phishing checks.' That is strong when-to-use guidance. It never states when NOT to use it or names an alternative sibling, so routing between this and dns_lookup/domain_report is left to inference.

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