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

Annotations cover the safety profile (readOnly, idempotent, non-destructive), and the description goes well beyond them: it discloses the data sources checked (live DNS, registry RDAP/WHOIS, a registrar), the confirmation guarantee before claiming availability, and the shape of the response including buy links and a citation URL.

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 tightly packed sentences, front-loaded with the usage trigger, then input modes, then sources and return contents. No filler; every clause carries information an agent needs.

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 explicitly (verdict per domain, buy links, tld.expert URL). Sources, TLD coverage and confirmation behavior are all specified, leaving nothing an agent must guess to invoke it correctly.

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 100% so baseline is 3, but the description adds genuine semantics: a full domain yields one verdict while a bare name fans out across popular or custom TLDs, which explains the otherwise non-obvious purpose of the two modes. It stops short of documenting the tlds list format, which the schema covers.

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 (check availability of a domain name) and immediately names the sibling concern it does not cover: it returns availability verdicts, not explanations or prices. An agent can distinguish it from explain_tld, get_tld_prices and suggest_tld_alternatives without reading further.

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?

Gives clear triggering conditions, including a literal user phrasing ("can I get <name>") and the two input modes. It does not explicitly route to or exclude sibling tools like suggest_tld_alternatives, so the guidance is clear but not fully disambiguated.

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