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

Beyond the readOnlyHint/openWorldHint annotations, it discloses the exact result vocabulary and the critical caveat that lists over 50 skip the registry, producing unconfirmed probably_available statuses. It also states the tool deliberately omits prices and premium status, which is behavior an agent cannot infer from annotations or schema.

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?

Purpose is front-loaded in the first sentence, followed by the status vocabulary and the escalation rules. The long parenthetical status list is information-dense and earns its place, though the packed parentheses and caps make it harder to scan than ideal.

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 an output schema present, return shapes needn't be spelled out, yet the description usefully adds the semantic interpretation and reliability differences among statuses — exactly the context a schema cannot convey. Nothing an agent needs to call this correctly and report results honestly is missing.

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 0%, so the description must carry the load: it explains the domains array with a hard limit of 200 and explains include_price's effect (adds premium and prices). The currency parameter is never mentioned, leaving one of three params undocumented anywhere.

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 whether domain names can be registered') and scopes the input ('a list of one or more names, up to 200'). It is clearly distinguishable from siblings like list_domains (existing registrations) and get_domain_pricing (prices).

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 explicit routing rules: use include_price for single names or lists up to 10, and 'always call get_domain_pricing for the chosen name' before purchase. It also describes the mandatory re-check workflow for probably_available results on lists over 50, covering when and when-not to trust a result.

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