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

No annotations are provided, so the description carries the transparency burden. It adds useful context about the default contact and when the setting is mandatory, but it does not disclose potential side effects like overwriting an existing contact, permission requirements, or whether the contact is verified. This is a moderate disclosure for a mutation tool.

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 sentences, front-loaded with the verb and object, and no wasted words. The explanation about purchase timing is relevant and concise.

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?

For a straightforward setter with fully documented schema parameters, the description provides enough context for tool selection and general usage timing. It does not describe return values, but no output schema exists and such detail is less critical here. The absence of annotations is partially compensated by the explicit guidance on when to use the tool.

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 input schema covers 100% of parameters with descriptions, so the baseline is 3. The description adds no parameter-specific detail beyond grouping them as 'WHOIS contact information,' which is appropriate but does not elevate the score.

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 clearly states the tool's function with a specific verb ('Set') and resource ('your WHOIS contact information'), distinguishing it from the sibling tool set_whois_privacy which handles privacy settings rather than contact 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?

The description explicitly says when to use it (for ICANN compliance and before transfers) and when it's not required (you can purchase domains without setting contact info first, using a default contact). This provides clear usage context and even notes the default behavior as an alternative.

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