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

Annotations already declare readOnlyHint and openWorldHint, and the description adds genuinely new behavioral facts beyond them: results are cached for 1 hour and each call costs $0.005, payable via x402 in USDC on Base or Solana. It stops short of describing error behavior, e.g. what is returned for an unregistered domain or a lookup timeout, so it is strong but not complete.

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 payload is front-loaded into a single dense sentence that lists the returned data, followed by short cache and price notes. Every clause carries information, though the mid-sentence enumeration runs long and could be split for faster scanning.

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 must convey what comes back, and it does so thoroughly across WHOIS, DNS, SSL, and risk flags. Payment and caching are covered; only failure/edge-case behavior is left unstated.

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 (name and tx) are already documented in the schema, which sets the baseline at 3. The description adds only indirect meaning by mentioning the x402 payment path, which loosely explains the tx parameter, but gives no extra syntax or format guidance for the domain name beyond the schema's pattern.

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 (domain) and enumerates exactly what is checked: WHOIS/RDAP registrar and dates, A/AAAA/MX/NS/TXT records, SPF/DMARC, HTTPS certificate, and risk flags such as a very young domain. This is clearly distinguishable from the other lookup siblings (email_check, evm_address, token_risk) because the resource and its return contents are named outright.

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?

Usage is only implied: an agent can infer this is the tool for domain registration/DNS/certificate reconnaissance and phishing screening. There is no explicit when-to-use or when-not, and no sibling alternative is named for overlapping needs (e.g., email_check for a mailbox on that domain).

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