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

Annotations only cover readOnly/openWorld, but the description adds high-value operational context: a per-call price ($0.01 USDC on Base), a hard auth requirement (x402-capable wallet client), and explicit exclusions (no contacts, no certificate details on Workers). These are exactly the behavioral traits structured fields do not 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?

Four tight clauses, front-loaded with the returned data, then exclusions, then cost and auth. No filler, and the highest-value constraints (price, wallet requirement) are stated plainly.

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 carries the return-value burden and does so by naming the record types returned. It also covers cost, auth, and unavailable data, so an agent has everything needed to decide and invoke correctly.

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 'domain' parameter is fully documented in the schema (public DNS domain, no URL path or contact data). The description's 'One public domain' reinforces the single-domain constraint but adds no syntax or format detail beyond the schema, so the baseline of 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?

The description enumerates exactly what the tool retrieves for a single public domain: sanitized RDAP registration data, DNS A/AAAA/MX/NS/CAA records, and verified HTTPS availability. That is specific enough to distinguish it from every sibling (none of which do domain intelligence), though it leads with a noun phrase rather than an explicit verb.

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?

Usage is implied by 'One public domain' and the enumerated data categories, so an agent can infer it is for single-domain reconnaissance. However, there is no explicit when-to-use, when-not, or named alternative, and no guidance on batching multiple domains.

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