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 covered. The description adds genuinely new behavioral context: a per-call price ($0.005) and the shape of the returned payload. It stops short of describing error behavior or failure modes for unregistered domains.

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?

Front-loads the returned fields, then cost, sample, and a return-path note. The closing 'Returns:' clause restates the field list from the opening sentence, which is mild redundancy, but the whole description is short and each element is scannable.

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 usefully summarizes the return payload and its nesting path, and adds pricing. For a one-parameter read-only lookup this is nearly sufficient; only error/empty-result behavior for invalid or unregistered domains is unaddressed.

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 parameter is fully documented as a bare domain name with an example. The description's sample payload repeats the schema's example rather than adding format nuance. Baseline 3 applies when the schema carries the parameter burden.

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 resource (the parsed WHOIS/RDAP record for a domain) and enumerates the fields returned: registrar, creation/expiry dates, nameservers, status codes. That is a concrete verbless-but-specific lookup. It does not, however, differentiate itself from siblings like domain_age or domain_profile, which apparently surface overlapping registration data.

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?

There is no statement of when to call this versus domain_age, domain_profile, or domain_dns, which all touch adjacent domain-attribute territory. The only auxiliary information is pricing and a sample invocation, neither of which tells the agent when this tool is the right choice.

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