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

Annotations already indicate a read-only, open-world operation. The description adds valuable behavioral context: it specifies the data source for Korean resources (KISA/KRNIC) and discloses a cost of 100 points per call. This goes beyond the annotations and helps the agent anticipate important constraints.

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 core purpose stated immediately. It combines English and Korean to cover both audiences, and every sentence contributes either purpose, special-case behavior, or cost information. There is no redundant elaboration.

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 simplicity (one parameter, no output schema, read-only annotations), the description covers the essential aspects: purpose, supported input types, special data sources, and cost. It could theoretically detail output format, but for a standard WHOIS lookup this is not a significant gap.

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 description already covers domain or IP input, achieving 100% coverage. The tool description enhances this by indicating that AS numbers (e.g., AS9318) are also accepted, which is not mentioned in the schema. This additional semantic information raises the value beyond the baseline for high schema coverage.

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 performs a WHOIS lookup for a domain or IP address, returning registration and ownership information. It uses a specific verb ('lookup') and resource ('domain or IP'), and distinguishes itself from sibling tools like nslookup or ip_history by focusing on WHOIS registration data.

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 clear context on when to use the tool, including special handling for Korean domains, IPs, and AS numbers via KISA/KRNIC. It does not explicitly mention alternatives or exclusions, but the scope is well-defined, so no critical guidance is missing.

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