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

Annotations already declare readOnly, idempotent, openWorld, and non-destructive, so the safety profile is fully covered without the description. The description adds the field categories returned, which is mild context, but discloses nothing about rate limits, auth, or lookup failures -- acceptable given the rich annotations.

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?

Two tight sentences with zero waste; the core capability is front-loaded before the relational note. Nothing should be cut.

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 an output schema present, return values needn't be explained, and the single required parameter is fully described. The only gap is the missing when-to-use guidance relative to sibling lookups, which matters given the dense sibling set.

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% and the domain parameter is fully documented in the schema (bare domain, punycode, no protocol/path/port), so the description correctly does not duplicate it. Baseline 3 applies because the schema carries all parameter meaning.

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 (Return) and resource (WHOIS/RDAP registration data) and enumerates the payload (registrar, dates, status, nameservers), so the agent knows exactly what it retrieves. It gestures at a sibling with 'Related: dns' but does not differentiate from the more ambiguous neighbors registrar, domain_changes, or epp_status.

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?

'Related: dns' is the only usage cue and it neither states when to prefer this tool nor when to avoid it. No exclusions or prerequisites are given, so the agent must infer that this is the raw registration lookup versus the registrar/status-specific siblings.

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