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

With no annotations, the description must carry the behavioral burden. It does disclose the cost (1 credit) and the data categories returned, which is useful, but says nothing about errors for unregistered or unsupported TLDs, rate limits, or authentication needs.

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 compact fragment that front-loads the resource and the protocol, then lists return categories and cost. No filler; only minor loss from the terse fragment style rather than full sentences.

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?

For a single-parameter lookup with no output schema, the description usefully enumerates what comes back, substituting for the missing output schema. Remaining gap is failure-mode behavior (no RDAP record, invalid domain), which matters for a lookup 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?

Single parameter with nominal 100% schema description coverage, so baseline 3 applies. The schema text is bare ("string, required") and the description only implicitly indicates the parameter is a domain name, adding little format guidance beyond the schema.

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?

Names a specific resource (domain registration data) and the protocol (RDAP) plus the concrete fields returned (registrar, dates, status, nameservers). It is readily distinguishable from siblings like ssl_check, though it never explicitly contrasts with 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?

Usage is only implied: an agent can infer this is for looking up registration/whois-style data for a domain. There is no explicit when-to-use statement, no exclusion of cases better served by ssl_check, and no note on domains without RDAP coverage.

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