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

Annotations already declare readOnly/idempotent/openWorld/non-destructive, and the description adds genuinely new behavior: the default TLD set, the per-domain status vocabulary (available, registered, unsupported, unavailable), what fields registered entries carry, that costs appear only when Cloudflare Registrar returns them, and that results are indicative and exclude owner details and trademark checks. These are exactly the limits an agent must know before reporting results to a user.

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?

Front-loaded with the usage trigger, followed by parameter constraints and then return shape; every sentence carries information. It is slightly long, and the return-value sentence partially duplicates the existing output schema, but nothing is wasted.

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?

For a read-only lookup tool with a full output schema and complete annotation coverage, the description supplies everything else an agent needs: trigger conditions, input limits, default TLD expansion, status vocabulary, and explicit caveats about cost accuracy and absent ownership/trademark data.

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% and the schema already documents both parameters, including maxItems, the default TLD list, and the distinction between bare names and full domains. The description restates the 5-name limit and default TLDs but adds no syntax or format detail beyond the schema, so the baseline of 3 applies.

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 states a specific verb and resource (check availability of domains and startup names) and is immediately distinguishable from the unrelated siblings (get_feedback_reply, index_tools, submit_feedback). It also pins down the scope of what is checked (default six TLDs) rather than leaving the resource generic.

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?

It gives an explicit trigger ("Use this when the user asks whether a domain or startup name is available or taken") plus three concrete user-utterance examples, covering both domain and bare-name phrasings. No sibling is a plausible alternative for this task, so the absence of a "when not to use" clause does not leave a real gap.

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