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

Annotations already declare readOnlyHint, idempotentHint, and openWorldHint, so the safety profile is covered; the description earns credit for adding the RDAP data source, the four possible status values, the semantic caveat on 'not_found,' and the explicit note that no price is returned. It stops short of mentioning lookup latency or rate limiting, which keeps it from a 5.

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 tight sentences, front-loaded with what is looked up, followed by return values and then the misinterpretation warning. No filler or repetition of the schema.

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 supplies the return-value vocabulary (registered/not_found/unknown/unsupported) and the key semantic caveat an agent needs to reason over the result. For a one-parameter read-only lookup, nothing material is missing.

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 0% for the single 'domain' parameter, so the description must carry the burden; the example 'yourbusiness.com' gives an implicit format cue, but it never states whether bare domain, subdomain, IDN, or URL input is accepted. Partial compensation only.

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 whether the domain registry has a registration record for a name') and names the data source (RDAP). It is plainly distinct from every sibling (create_website, list_websites, get_website, etc.), none of which deal with registry records.

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 establishes the use case clearly—checking registry data for a domain name—and explicitly warns that 'not_found means no record was found: it does not mean the name can be bought,' which prevents the obvious misuse. No alternative tool is named, but no sibling overlaps this function, so there is little to route to.

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