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

Annotations already declare readOnly/openWorld/non-destructive, so safety is covered; the description adds real value by bounding scope ('Public records only; owner contact details are not returned') and by listing the data surfaces an agent can expect. It does not say what happens for unregistered or unparsable domains, which is the remaining behavioral gap.

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?

A single front-loaded sentence that opens with the usage trigger and then enumerates the returned record types; each clause conveys distinct information about output, and the scope caveat closes it cleanly with no filler.

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 carries the return-value burden and does so by enumerating record categories plus the exclusion of owner contact data. Only the failure/not-found behavior is left unspecified, which is minor for a read-only lookup.

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 coverage is 0% and the single 'domain' parameter has no type/format detail in the schema beyond 'string'. The description compensates partially by implying one existing, registered domain (not a list, not a TLD), but it never shows the expected form (e.g. bare 'example.com', no scheme or path).

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+resource (look up one existing domain's public records) and enumerates exactly what is returned: registrar, registration/expiry dates, lock status, nameservers, DNS host, MX/SPF/DMARC, HTTPS reachability. The phrase 'one existing domain' implicitly separates it from list-oriented siblings like search_domains and suggest_domains, but no sibling is named explicitly.

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?

'Use this when someone asks about one existing domain' gives a clear triggering condition and the singular scope rules out the search/suggest siblings. It does not spell out when-not-to-use or explicitly name get_tld_info/screen_domains as alternatives, which keeps it one notch below the top.

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