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

Beyond the supplied annotations (readOnly, openWorld, non-idempotent, non-destructive), the description discloses the payment model and pricing, the exact failure mode for unpaid calls (isError plus a fresh invoiceId in a PaymentRequired object), the retry mechanism, and the shape of the returned data (resolver id, rcode, TTLs, query_ms, observed_at). This is unusually rich behavioral context for a paid, network-dependent call.

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 pricing and paid-call mechanics are front-loaded, then the purpose and return fields, then the payment retry flow — a sensible order with dense, purposeful sentences. It is slightly long, and the pricing detail duplicates information already present in the title, but nothing is genuinely wasted.

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?

For a three-parameter, network-dependent paid tool with no output schema, the description covers everything an agent needs: what is queried, what comes back, what happens without payment, and how to complete payment. No significant gap remains.

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, types, and payment_signature, including the allowed record types and the instruction to omit the signature on the first call. The description reinforces the payment loop around payment_signature but adds no syntax or format detail beyond what the schema provides, so the baseline 3 is appropriate.

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?

The description names a specific verb and resource (reads raw DNS records for a given FQDN and record types) and frames the single question it answers: 'What DNS records does this name return right now?' It also enumerates the record types and returned fields, so an agent can tell it apart from the payment/ledger siblings without opening the 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?

It gives clear usage context: it is a per-call paid DNS lookup, unpaid calls fail with an x402 PaymentRequired object, and the agent should retry with a signed payload in _meta["x402/payment"] or via the payment_signature argument. It does not explicitly name alternatives or exclusions, but the sibling set contains no overlapping DNS tool, so the only real gap is the absence of an explicit 'do not use for X' statement.

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