lookup_domainLooks up one domain in WHOIS/RDAP and returns whether it is registered, its expiry and registration dates, days until expiry, registrar, status codes and nameservers. Results may be cached for up to 48 hours. Does not need a TLDix account.
| Name | Required | Description | Default |
|---|---|---|---|
| domain | Yes | Domain name, e.g. example.com. A URL or www. prefix is accepted and stripped. |
Changes observed during successful MCP inspections.
Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already declare readOnly, openWorld, idempotent and non-destructive, so the safety profile is covered. The description adds real context beyond them: the upstream data sources (WHOIS/RDAP), a staleness caveat ('cached for up to 48 hours'), and that no account is required — all of which materially affect how an agent should trust and interpret results.
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?
Three sentences, front-loaded with the action and the return set, then the two operational caveats (caching, no account). Nothing is redundant and nothing is buried.
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 carries the return-value burden and does so well by enumerating the fields. Minor gaps remain around edge cases — behavior on an invalid or malformed domain, and any rate limiting — but for a single-parameter read tool it is nearly complete.
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 coverage is 100% and the single parameter already documents format, URL acceptance and www stripping, so the description needn't compensate. It adds no parameter detail at all, which is the baseline-3 case rather than a 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?
States a specific verb and resource ('Looks up one domain in WHOIS/RDAP') and enumerates exactly what comes back: registration status, expiry/registration dates, days until expiry, registrar, status codes, nameservers. The word 'one' plus the enumerated return set distinguishes it from list_tracked_domains and add_domain without opening either 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?
Usage is implied by the purpose ('look up a domain'), and 'Does not need a TLDix account' gives a useful precondition, but there is no explicit when-to-use/when-not guidance and no reference to the obvious alternative, check_domain_expiries, which an agent could easily confuse this with.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.
Add one secure layer between your agents and this server.