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

Annotations already establish read-only, idempotent, non-destructive behavior, so the bar is lowered. The description still adds real value: it defines what each result state means and warns that a failed check must not be treated as available, which is non-obvious failure semantics an agent could otherwise get wrong.

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 first sentence front-loads purpose and scope, and the status glossary is compact and information-dense rather than padded. The enumeration is slightly long, but every clause defines a distinct state the caller must interpret.

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-shape explanation is unnecessary, and the description instead supplies the interpretation layer for the status values plus failure semantics. The only real gap is guidance on when to prefer this over a single-domain or monitoring alternative.

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?

There is a single parameter with 100% schema description coverage, so the schema already documents format and the 50-domain cap. The description only echoes the limit and adds no syntax or format detail beyond the schema, making the baseline 3 correct.

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 the registration status of ... domains') and adds scope ('up to 50', 'at a point in time'). It is clearly distinguishable from status-oriented siblings like available or tld_check, though it never names the single-domain sibling it complements.

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?

Bulk usage is strongly implied by 'up to 50 domains' and 'at a point in time', which hints this is a snapshot rather than a monitoring tool. However, there is no explicit when-to-use, when-not-to-use, or named alternative (e.g. available for a single domain, monitor for ongoing tracking).

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