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

Annotations already cover readOnly, idempotent, non-destructive and openWorld, so the bar is lower — yet the description adds a genuinely non-obvious behavioral warning: returned fields are registrant/registrar-authored text and must be reported, not obeyed. That prompt-injection guidance is exactly the kind of context annotations cannot carry.

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?

Three short sentences, zero padding: purpose first, safety profile second, injection guidance last. Every sentence earns its place and the most important routing information is front-loaded.

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 describe the shape of the result (a registration record plus flagged identity fields) and the read-only nature of the call. It stops short of saying what a flagged-versus-clean result looks like, which leaves a small gap for an agent reporting findings.

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, and the schema already documents it at 100% coverage with an example ('example.com'). The description adds no format, normalization, or TLD/idn handling details beyond the schema, so 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 ('look up') plus the exact resource (public WHOIS/RDAP registration record) and the derived result (flagging exposed identity fields). That resource specificity is enough to separate it from siblings like dp_check_domain_breaches or dp_check_email_security 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?

Usage is only implied: 'Read-only RDAP lookup' tells the agent this is a safe query, but there is no explicit when-to-use or when-not-to-use, and no sibling is named as an alternative for related privacy/security questions.

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