Look up a domain's WHOIS registration record: registrar, creation and expiry dates, days remaining, name servers, and domain statuses, direct from the TLD registry. Registration data only — for DNS/mail health as well, use domain_health_check; for a combined report, use domain_report.
| Name | Required | Description | Default |
|---|---|---|---|
| domain | Yes | Bare domain to look up, e.g. example.com (no scheme/path) |
Changes observed during successful MCP inspections.
Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
No annotations are provided, so the description carries the full burden. It usefully discloses the data source ('direct from the TLD registry') and the exact fields returned, but says nothing about edge cases an agent would care about: unregistered/expired domains, rate limits, or lookup failures. Adequate but incomplete for a tool with zero annotation coverage.
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, no waste. The output-field enumeration and the sibling routing rule are both front-loaded, so the agent gets scope and alternatives before any schema inspection.
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 compensates by enumerating the returned fields, which is exactly what the agent needs to interpret results. The only gap is behavior for unregistered or lookup-failure cases, which is a minor omission for a simple read 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?
Schema description coverage is 100% and the single parameter's format constraint ('bare domain, e.g. example.com, no scheme/path') is already documented in the schema. The description adds no syntax, format, or validation detail beyond that, so the baseline 3 applies.
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 (look up) and resource (domain WHOIS registration record), then enumerates the exact fields returned: registrar, creation/expiry dates, days remaining, name servers, statuses. It explicitly distinguishes itself from domain_health_check and domain_report, so an agent can route without opening another schema.
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?
Explicitly bounds scope ('Registration data only') and names both alternative tools with the condition that selects each: domain_health_check for DNS/mail health and domain_report for a combined report. Nothing is left to inference.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.
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