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

With no annotations provided, the description carries the full burden. It discloses the default limit of 100, lists exactly what fields appear in each result, and defines the availability phases. This is meaningful behavioral context, though it omits ordering, authentication, and error behavior.

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 description is four sentences with no waste: it states the purpose, lists filters, highlights the default limit, summarizes result fields, and defines availability values. The cost note is extra but useful. Every sentence earns its place.

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?

Given the tool's moderate complexity (5 optional params, no required params) and the presence of an output schema, the description is quite complete. It covers filtering, pagination, defaults, and result contents. It merely lacks an explicit pointer to sibling tools, but that is not essential for basic usage.

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 100% and every parameter already has a clear description, so the baseline is 3. The description adds a bit of interpretive value by restating the limit default and defining availability values, but these duplicate schema information rather than providing new semantic depth.

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 opening sentence 'List or search top-level domains (TLDs) with registry metadata' clearly states the action and subject. It distinguishes this from single-TLD lookup tools like domains.tld_details, although it does not explicitly name any sibling tools.

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?

The description explains when to use the tool by outlining its filters (substring, availability, category) and pagination options. However, it never mentions alternatives or says when not to use this tool, leaving the comparison with nearby tools like domains.tld_details or domains.check_availability implicit.

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