Look up a domain registration

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

Annotations already declare readOnlyHint=true and openWorldHint=true, so safety and external-call behavior are covered. The description does add the upstream sources (RDAP with a WHOIS fallback), which is meaningful context, but it says nothing about rate limits, failure modes for unregistered domains, or latency.

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?

A single front-loaded sentence that names the sources first and then the returned fields. No redundancy, no filler, and the most decision-relevant information leads.

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 usefully enumerates the returned fields and the data sources, and annotations carry the read-only/open-world profile. It stops short of describing error behavior (e.g., domain not registered) or which source was used in a given response, which would complete the picture.

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%, so both 'domain' (host/URL reduced to registrable domain) and 'raw' (includes raw WHOIS text on fallback) are already fully documented in the schema. The description adds no parameter-level meaning 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 and resource ('Returns the registration record of a domain') and enumerates exactly what the record contains (registrar, dates, status codes, nameservers, abuse contact). The RDAP/WHOIS framing cleanly separates it from siblings such as lookup_dns or inspect_ssl_certificate without needing to name them.

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?

There is no when-to-use versus when-not-to-use guidance and no alternative tool is named. An agent must infer from the sibling list whether registration data is what it wants. Nothing about prerequisites or fallback conditions is stated.

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