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

No annotations exist, so the description must carry the full behavioral burden. It does disclose the resolver backend (Cloudflare DoH), the public-DNS-only limitation, and the per-call cost of $0.001 USDC, but says nothing about the response shape, failure modes (NXDOMAIN, timeouts), or whether lookups are cached.

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?

Purpose and scope are front-loaded in the first two clauses, and the examples are compact. The tail of pricing plus three cross-sell endpoints is denser than strictly necessary and reads partly as marketing, though it does double as routing information.

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 and no annotations, the description must cover both invocation and result interpretation. It handles invocation well (types, examples, public-only scope) but leaves the return format and error behavior undefined for an agent that needs to parse results.

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 0% — neither param carries a description or enum — so the description does real work by giving concrete call examples and enumerating the valid `type` values. The remaining gap is what happens when `type` is omitted (default A? all types?), which is left unstated.

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 and resource ('DNS resolve via Cloudflare DoH') and enumerates the exact record types supported (A/AAAA/MX/TXT/NS/CNAME), which lets an agent separate it from domain_lookup, ens_lookup, or email_check without opening a 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?

Includes an explicit scoping constraint ('Public DNS only') and names the sibling endpoints for adjacent needs — RDAP age/registrar via /domain, TLS/SPF/DMARC posture via /check, and mailbox validation via /email-check — each with its price. It stops short of an explicit 'use this when / do not use it for X' statement, but the routing intent is clear.

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