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

Annotations already cover the safety profile (readOnlyHint, openWorldHint), and the description adds real context beyond them: the DNS-over-HTTPS transport, TTL inclusion, DNSSEC presence via DNSKEY/DS, and the resolver validation flag. It does not mention rate limits or failure behavior (e.g. NXDOMAIN handling), which keeps it short of a 5.

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?

Two tight sentences, front-loaded with the capability and record types before the audience note. The final 'for domain research, due diligence and infrastructure agents' phrase is mild positioning rather than load-bearing information, but nothing is redundant or bloated.

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 does the work of describing returns by naming record types, TTLs and DNSSEC artifacts, which is sufficient for a single-parameter lookup. Error cases (nonexistent domain, timeout) are the only notable omission.

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?

Only one parameter exists and schema coverage is 100%, with the schema already documenting 'Domain name without scheme.' The description adds no syntax, IDN, or subdomain guidance beyond that, so this is the baseline case where the schema carries the meaning.

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 (DNS lookup) and resource (a domain's DNS records), and enumerates exactly what is returned: A, AAAA, NS, MX, TXT, CAA, SOA, CNAME with TTLs, plus DNSSEC (DNSKEY, DS) and the resolver validation flag. No sibling tool overlaps this capability, so an agent can select it unambiguously.

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 closing clause 'for domain research, due diligence and infrastructure agents' implies when the tool is useful, but there is no explicit when-to-use rule, no prerequisites, and no named alternative or exclusion relative to siblings like email_auth or site_audit. Usage is inferred rather than stated.

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