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

With no annotations, the description carries the full burden and does disclose important traits: live (uncached) DNS, no API key/account needed, and a per-call cost of $0.005 paid via x402 (USDC). Cost and payment model are exactly the kind of context an agent needs. It omits rate limits, timeouts, and error behavior, and does not define the "looks parked" heuristic.

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?

Four sentences, front-loaded with the payoff (everything DNS in one call), followed by usage pattern, constraints, and pricing. Every sentence adds distinct information with no filler.

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?

There is no output schema, so the description correctly substitutes by enumerating the returned fields, and it covers auth, cost, and usage pattern. It lacks any note on response shape, pagination (not applicable here), or failure behavior, which keeps it from a 5.

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% and the single parameter is fully documented in the schema (URL/email reduced to host). The description adds no parameter-level detail, so the 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 resource (DNS data for one domain) and enumerates exactly what is returned: registration status, A/AAAA, nameservers, MX, SPF/DMARC, DNSSEC, parked heuristic. That enumeration implicitly separates it from siblings like red_whois (registration data) and red_dnsbl (blocklists) without the agent opening any 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?

"Built for going through a list of domains one at a time" gives clear context for how and when to invoke it (one domain per call, iterating over a list). It does not name alternative tools or state exclusions, so it stops short of a 5.

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