whois_domainRetrieve domain registration details—registrar, creation/expiration dates, and nameservers—via RDAP to identify domain ownership and infrastructure.
Domain registration data (registrar, dates, nameservers) via RDAP.
| Name | Required | Description | Default |
|---|---|---|---|
| domain | Yes |
| Name | Required | Description | Default |
|---|---|---|---|
| result | Yes |
Changes observed during successful MCP inspections.
v0.1.0Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already carry readOnlyHint, openWorldHint, idempotentHint, and destructiveHint false, so the safety profile is covered. The description adds useful context by noting the data comes via RDAP and naming the returned data types, but it doesn't disclose rate limits, RDAP edge cases, or error behavior. There is no contradiction with the 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?
The description is a single compact sentence with no filler, and the main data categories are listed in parentheses. It could be improved with an explicit verb and a more front-loaded structure, but for a simple lookup tool the size is appropriate.
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 rich annotations, a single obvious parameter, and an output schema present, the description is largely sufficient for tool selection and invocation. It conveys the data categories and protocol, and the safety profile is already covered by annotations. The primary missing element is parameter formatting, which is already captured under parameter semantics.
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 0%, and the only parameter 'domain' is a bare string with no format guidance. The description never states whether the value should be a bare registrable domain, include a subdomain, or use punycode, so an agent may pass an invalid value. Because the description must compensate for the low schema coverage, this is a meaningful gap.
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 identifies the resource (domain registration data) and the mechanism (RDAP), and lists specific data categories: registrar, dates, and nameservers. It doesn't use an explicit verb like 'retrieve', but the intent is unambiguous. It is also distinguishable from sibling whois_ip because it focuses on domains rather than IP addresses.
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 implies usage is for domain registration metadata lookups, which is a clear enough context. However, it does not explicitly mention alternatives such as whois_ip or dns_lookup, and it does not state when not to use this tool. The sibling list provides context, but the description itself offers no routing guidance.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.