lookup_domain

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

No annotations are present, so the description carries the behavioral burden. 'Look up' and the caveat 'available RDAP registration data' convey a read-oriented query and hint that RDAP data may be absent, but the description does not disclose failure modes, data source, rate limits, or return structure.

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?

One sentence, front-loaded verb, and no filler; every phrase contributes either the record types or the RDAP caveat. This is an efficient, scannable definition.

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 one simple parameter and no output schema, the description is adequate for basic tool selection, but it omits what the returned DNS/RDAP data looks like and any error or availability edge cases. An agent can invoke it, but cannot fully predict output variability.

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?

The schema provides only a `domain` string with 0% description coverage. The description repeats that the tool operates on domain names but never specifies the expected format (e.g., bare domain, no protocol, no trailing slash) or whether IDNs/punycode are accepted, so it adds little meaning beyond the parameter name.

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 names a concrete verb ('Look up') and specific resources (A/AAAA/MX/NS/TXT records and RDAP data), so the tool's domain scope is clear. The explicit record-type list also differentiates it from sibling lookup tools like lookup_shodan_host, which focus on Shodan data.

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 record types give an implied use case: call this when DNS or RDAP registration data is needed for a domain. It does not explicitly state when not to use it or name alternatives such as lookup_shodan_host or search_web, so routing guidance is left mostly to inference.

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