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

With no annotations, the description carries the full burden for behavioral disclosure. It indicates a read operation ('Look up') and describes the output fields (registrar, status, dates, nameservers, contacts). It does not mention the WHOIS fallback, error behavior, rate limits, or response format, which would provide richer transparency, but the core read-only nature is clear.

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 well-structured sentence, front-loaded with the action ('Look up') and the resource ('normalized RDAP registration data'). It covers the key output categories without unnecessary words or repetition.

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?

Given it has no output schema, the description lists the main data categories returned, but omits the response structure and error scenarios. The parameter schema compensates for configuration details. The tool is simple enough that this is adequate, but the lack of any usage or fallback context in the main description keeps it at a minimum-viable level.

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 the parameters are well documented. The main description adds no additional parameter meaning, but the schema already explains domain, whois, and follow thoroughly, including defaults and behavioral consequences. The baseline of 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?

The description uses a specific verb and resource: 'Look up normalized RDAP registration data ... for a domain name.' It clearly identifies the tool's purpose and distinguishes it from IP, ASN, and entity lookups in the sibling list. However, it does not explicitly differentiate itself from bulk-domain-lookup, so it falls short of a 5.

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 gives no guidance on when to use this tool versus alternatives. It does not mention bulk-domain-lookup, tlds, or other siblings, nor does it state any exclusions or prerequisites. The whois and follow parameter descriptions imply some configuration choices, but tool selection guidance is entirely absent.

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