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

Annotations already declare readOnly, idempotent, openWorld and non-destructive, so the safety profile is covered. The description adds substantive context beyond that: data provenance (RDAP registry, no scraping), the extra live-zone nameserver comparison and DNSSEC check, and graceful degradation when a ccTLD lacks RDAP. It stops short of rate-limit or error semantics.

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 sentences, front-loaded with the core action and data source, and each following sentence contributes a distinct fact (extra checks, subdomain rule, ccTLD limitation). Slightly dense with enumerations, but 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?

There is no output schema, so the description carries the burden of describing results – and it does, listing the registry fields, status locks, danger states, nameservers and the DNSSEC/zone comparison. Combined with the annotations, an agent has everything needed to call it and interpret the response.

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 100%, so both parameters – including the URL/email normalisation of 'domain' and the summary/full enum – are already fully documented. The description adds no parameter-level meaning beyond the schema, which is the expected baseline 3.

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 specific verb and resource (read a domain's public registration record) and pins the mechanism (RDAP, not WHOIS scraping). It enumerates the exact fields returned – registrar, creation, expiry, status locks, danger states, nameservers – so an agent can distinguish it from check_email_auth, check_ssl and check_security_headers without opening a schema.

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 context is implied by the 'check' framing and it clarifies edge behaviour (subdomains are resolved to their registered domain; ccTLDs without RDAP are reported). However, it never states when to prefer this over the sibling full_domain_report, which likely subsumes it, and gives no exclusions or prerequisites.

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