Look up WHOIS registration data for a domain to get registrar, creation and expiration dates, name servers, and contact information.
Look up WHOIS registration data for a domain. Returns registrar, creation date, expiration date, name servers, and contact info.
| Name | Required | Description | Default |
|---|---|---|---|
| domain | Yes | Domain name (e.g., "github.com"). Without https:// |
Changes observed during successful MCP inspections.
v1.4.2Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already declare readOnlyHint=true and openWorldHint=true, so the agent knows this is a safe, read-only operation. The description adds the specific data fields returned but does not disclose any additional behavioral traits such as rate limits, latency, or data freshness. With annotations covering the safety profile, the description provides modest added context, warranting a score of 3.
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 a single, front-loaded sentence that states the action, the resource, and the key return fields without any filler. Every word contributes to understanding, making it highly concise and well-structured.
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 simple one-parameter tool with annotations covering safety and schema covering the parameter, the description is complete. It lists the primary return fields, and since there is no output schema, this suffices for an agent to understand what to expect. No critical information is missing.
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 schema covers 100% of the single parameter (domain) with a description that clarifies the expected format (e.g., 'github.com' without 'https://'). The tool description does not add extra semantic detail beyond what the schema already provides, so the baseline score of 3 is 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?
The description clearly states the tool's purpose with a specific verb ('Look up') and resource ('WHOIS registration data for a domain'), and enumerates the expected return fields (registrar, dates, name servers, contact info). It is distinct from sibling tools like dns_lookup or check_ssl, making its purpose unambiguous.
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 does not provide any guidance on when to use this tool versus alternatives. It does not mention exclusions, prerequisites, or typical use cases. An agent must infer from the name alone, which may be insufficient for selecting between related lookup tools.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.