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

Beyond the readOnly/idempotent/openWorld annotations, the description discloses the return shape (clean JSON with TTLs, NXDOMAIN flag, DNSSEC-authenticated bit), input normalization (URL/email reduced to host), and critically the paid x402 flow requiring a first call for the PaymentRequired object then a retry with _meta["x402/payment"]. That is exactly the operational context annotations cannot convey.

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-loaded with verb+resource and packed densely with high-value details (record types, return shape, payment flow). Slightly redundant in re-listing enum values already in the schema, but no wasted sentences.

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?

No output schema exists, so the description carries the burden of describing return values (TTLs, NXDOMAIN flag, DNSSEC bit) and it does so. It also covers the non-obvious payment handshake, which is the riskiest part of invoking this tool, leaving nothing essential missing.

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%, so the schema already documents 'name' and the 'type' enum including the ALL default set. The description mostly restates the enum contents (SRV, PTR, DS, DNSKEY, HTTPS) rather than adding meaning, 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 verb (resolves) and resource (live DNS records for any domain or hostname) plus the resolver used (1.1.1.1) and the record types covered. An agent can distinguish it from siblings like email_auth_check or whois_domain_age without 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?

Gives clear triggering contexts: verify a domain, find mail servers or nameservers, read TXT/SPF records. It does not, however, explicitly name sibling alternatives or state when NOT to use it (e.g. vs email_mx_verify for mail checks), so the routing guidance is contextual rather than complete.

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