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

Annotations already declare readOnlyHint=true, destructiveHint=false and idempotent, so the safety profile is covered; the description adds that results come from a live check, include 'taken and unknown' statuses, may be unordered/filtered (left_out, unchecked_names), and that the search is advisory only. The final 'Read-only, no side effects' sentence merely restates the annotations, which caps it below 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?

The purpose is front-loaded, which is good, but the body is two enormous run-on sentences chaining together output-field explanations; the density makes it harder to scan than necessary. It is not padded with fluff, but the structure could be split so an agent can locate the top_picks vs suggestions distinction quickly.

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 6 parameters, full schema coverage, an output schema and rich annotations, this description already carries more than the minimum, and the advisory/purchase caveats are genuinely important context for a domain-search tool. It over-explains return fields that the output schema already documents, so it is complete but slightly redundant rather than optimally scoped.

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 already 100%, so baseline is 3, but the description adds real meaning: 'up to limit ranked names', 'never repeating a top pick', per-year USD pricing tied to years, and that each entry in tlds becomes a top pick and reports why it found nothing. That goes beyond the schema field text for tlds, limit and include_premium.

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 ('Find domain names') plus the input shape it accepts (free-text idea, brand, phrase) and the derivation rule (short combinations of its words). It also names the sibling it complements — 'confirm the chosen name with check_domain' — so an agent can separate search from single-name verification without opening another 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?

Gives clear when-to-use framing (starting from a free-text idea rather than a known domain) and an explicit handoff rule to check_domain before quoting, plus the note that a purchase re-checks. It stops short of naming when NOT to use it — e.g. checking one already-known domain, or the check_transfer/get_tld_requirements siblings — so the exclusions are inferred rather than stated.

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