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

Annotations already declare readOnlyHint=true, but the description adds valuable context: 'currently registered' aligns with openWorldHint (live data), non-domain input returns an error, and a per-call point cost is disclosed. These behavioral traits go beyond the 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 compact and front-loaded with the primary purpose, followed by error behavior and cost. It is bilingual, creating slight redundancy, but every element earns its place without unnecessary verbosity.

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 one-parameter tool with no output schema, the description covers the purpose, expected input format, error handling, and cost. It clearly communicates the return type (list of IP addresses), making it complete for effective selection and 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 input schema already describes the 'domain' parameter with an example (apick.app), so baseline is 3. The description adds meaning by clarifying that non-domain values will cause an error, which is a validation rule not present in the schema. This extra context raises the score above baseline.

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 states the tool's function: 'Resolve a domain name to its currently registered IP addresses (DNS lookup).' It specifies the verb and resource, and the input validation note distinguishes it from sibling tools like reverse_ip (IP-to-domain resolution).

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 use for domain-to-IP resolution but does not explicitly mention when to use it over alternatives such as reverse_ip or whois. The note about non-domain input returning an error provides some usage context, but no explicit when-not-to-use guidance is given.

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