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

Annotations already cover the safety profile (readOnlyHint=true, destructiveHint=false, openWorldHint=true), so the description's added value is the provenance-and-accuracy caveat: results come from DNS and public registry records and are advisory rather than authoritative. It also discloses the 500-item ceiling and the tlds=["all"] sentinel. It stops short of saying anything about latency or rate limits when screening 500 names, which is the main remaining unknown for a bulk call.

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 primary use case, then the caveat that governs trust in the results. No filler and no restatement of the title.

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 adequately by naming registration status, registrar, and expiry date. The one substantive gap is that it never clarifies which of the two input shapes to use (bulk domains list versus one name across tlds), which matters for a 4-parameter tool with no required fields.

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 75%, so the schema already documents name, tlds, and details. The description adds real meaning for the tlds=["all"] sentinel and the 500 cap, and implies details via 'with its registrar and expiry date'. However, the `domains` parameter has no schema description and the description never explains the name+tlds versus domains calling modes, leaving the most ambiguous input undocumented in both places.

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 — bulk availability screening of domain names — plus the data sources (DNS and public registry records) and what is returned (registration status, registrar, expiry). It also explicitly contrasts itself with search_domains, so an agent can separate it from the four siblings without inspecting any 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 a clear use case (many names at once, up to 500, or one name across all endings), and an explicit when-not: this is a quick screen, not the registrar's answer, so names intended for a suggestion should be confirmed with search_domains. The alternative and the condition that selects it are both named.

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