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

Annotations already indicate read-only and open-world behavior, and the description adds value beyond that by stating that invalid non-domain inputs return an error and that results reflect currently registered IPs. It does not mention empty-result handling or DNS resolver details, but those are minor for a simple read-only tool.

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 appropriately short and front-loaded, with the core action in the first sentence followed by validation behavior and cost. No unnecessary background or fluff is included.

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 one-parameter, read-only DNS lookup with no output schema, the description provides enough context: what input is required, what output to expect (list of currently registered IP addresses), and what error to anticipate for invalid input. Nothing essential is missing.

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 only parameter, domain, already has 100% schema coverage with a clear description and example (apick.app). The tool description reinforces that the value must be a domain, but it does not add substantial meaning beyond the schema.

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 uses a specific verb and resource: 'Resolve a domain name to its currently registered IP addresses (DNS lookup).' This clearly distinguishes it from sibling tools such as reverse_ip (IP-to-domain lookup) and whois (domain registration metadata).

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 use case is explicitly clear: invoke it when given a domain and needing its current IP addresses. It also states that non-domain values produce an error, which is a useful when-not-to-use signal. However, it does not explicitly mention alternatives like reverse_ip or whois.

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