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

Annotations already mark readOnlyHint and openWorldHint, but the description adds material behavior: RDAP bootstrap behavior, redaction of registrant contact data, x402 pricing, accepted payment chains, and that failed calls are not charged. These details go well beyond structured fields.

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 description is front-loaded with returned facts, then the redaction caveat, then cost and payment details. Three tight sentences, each earning its place for a paid lookup tool.

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?

An output schema exists and annotations cover safety and open-world status, so the description need not explain return structure. It still supplies enough context about RDAP source, redaction, and billing to set expectations.

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?

The single domain parameter is fully documented in the schema with an example, so schema coverage is 100%. The description adds no syntax or format constraints beyond what the schema already provides, making the baseline 3 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?

States the exact resource and method: domain registration facts via RDAP, and enumerates dates, registrar, status flags, nameservers, and DNSSEC delegation. This is clearly distinct from DNS-resolution and reputation siblings such as security_dns_records, even though it does not name alternatives.

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 only implied by the resource description; there is no explicit when-to-use guidance, no exclusions, and no named alternatives. An agent can infer it is for registration data, but must decide on its own versus DNS, typosquatting, or other domain-security tools.

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