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

Annotations already declare readOnlyHint=true, openWorldHint=true, and destructiveHint=false. The description adds useful context that the lookup is live and not persisted, but it does not cover external-service failure modes, rate limits, or response behavior.

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 front-loaded sentence with no wasted words. It states the core action and the non-persistence constraint immediately.

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 simple one-parameter lookup, annotations cover the safety profile and the description covers live/non-saved behavior. However, it leaves the domain input format and what registration-expiry data is returned unstated, and there is no output schema to fill that gap.

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%, so the description must explain the single 'domain' parameter. 'any domain' is minimal and does not clarify accepted format, whether protocols/subdomains are allowed, or examples such as example.com.

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 states a specific verb and resource: a live RDAP/WHOIS lookup of a domain. The title adds that it retrieves registration expiry, but the description itself does not explicitly distinguish this from sibling lookup tools such as lookup_cert or lookup_ct beyond the implicit 'domain' resource.

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?

It gives no explicit when-to-use guidance, prerequisites, or alternatives. '(not saved)' hints that this is a transient lookup, but no sibling or saved-asset path is named to help an agent choose between them.

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