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

Annotations already cover read-only, open-world, idempotent, and non-destructive behavior. The description adds that the tool returns DNS records with values and TTLs, which is minimal additional context about the response content. It does not mention rate limits, authentication nuances beyond the schema, or other behavioral details, so it adds modest value over annotations.

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 concise sentence that front-loads the purpose and record types, followed by a clear usage example. There is no fluff or redundant content; every element earns its place, making it highly efficient for an agent to parse quickly.

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 simple lookup tool with complete parameter schema and annotations covering safety, the description sufficiently explains what the tool returns (DNS records with values and TTLs) and provides a usage example. It does not detail error handling or output shape, but given the tool's low complexity, the description is adequate 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?

Schema description coverage is 100% for both required parameters (domain and _apiKey). The description provides an example call with placeholders, reinforcing the schema but not adding new semantic details like input format constraints or validation rules. The baseline of 3 applies since the schema already documents the parameters adequately.

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 clearly identifies the tool as retrieving DNS records for a domain, listing common record types (A, AAAA, MX, NS, TXT) and mentioning values and TTLs. It effectively distinguishes from sibling WHOIS tools by focusing on DNS records, though it does not explicitly contrast with them. The purpose is specific and not a tautology of the name.

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 implies usage (if DNS records are needed, use this tool) but does not explicitly state when to use it versus alternatives like whoisxml_whois or whoisxml_reverse_whois. No exclusions or conditional routing is provided, leaving the agent to infer the appropriate context from the tool's purpose.

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