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

With no annotations provided, the description carries the full burden of behavioral disclosure. It transparently states that it queries each registry over RDAP, that 'unknown' can result from no RDAP server, timeouts, or 429s, and that 'not_registered' does not imply the name is for sale. It also discloses that each answer includes a price. This is thorough and goes beyond basic operation, covering edge cases and limitations.

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 a single dense paragraph but every sentence serves a purpose: purpose, input formats, answer semantics, and a caveat. It is front-loaded with the core question and method. There is no redundant or filler text. The length is justified by the necessary nuance around answer interpretation.

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 has only 2 parameters, no output schema, and no annotations, the description does a solid job of covering what an agent needs to know: how to format inputs, what the possible outputs are, and what each output means. It mentions the price field but does not detail the exact response structure (e.g., JSON keys). This is a minor gap, but the description is largely sufficient for correct invocation.

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?

The schema already describes both parameters with examples, and coverage is 100%. The description adds meaning by explaining the relationship between 'name' and 'tlds' (e.g., bare word plus tlds, or full names), which the schema does not fully clarify. It also explains the expected answer types. This adds value beyond the schema, though the schema is already descriptive.

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 opens with a clear, specific question 'Is a domain name registered?' and immediately states the method (RDAP). It distinguishes itself from sibling tools like get_tld or search_tlds, which focus on TLD metadata, by focusing on registration status. The scope is explicit and leaves no ambiguity about what the tool does.

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 provides explicit input formats (full name, bare word with tlds, comma-separated list) and explains the meaning of each possible answer (registered, not_registered, unknown), including caveats like reserved/premium domains. It does not explicitly name alternative tools for when not to use it, but the purpose is clear enough that an agent can infer when to call it. Slightly missing an explicit 'use X instead' but the guidance is strong.

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