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

Annotations already declare readOnlyHint and openWorldHint, so this is clearly a safe read operation. The description adds useful non-annotated context: Korean resources are queried via KISA/KRNIC original data, and each call costs 100 points. No contradiction exists.

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 short and front-loaded with the primary purpose. The bilingual repetition is somewhat redundant but understandable for a Korean-facing tool, and the cost note is compactly appended without disrupting clarity.

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 single-parameter read-only lookup with full schema coverage, the description covers the accepted input types, special Korean source behavior, output purpose, and cost. It does not detail output structure or error behavior, but that is not critical for invoking this tool correctly.

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 documents the single 'address' parameter with 100% coverage and an example. The description adds extra meaning by noting that AS numbers, such as AS9318, are also accepted and that Korean .kr/.한국 domains and domestic IPs resolve through KISA/KRNIC.

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 states a specific verb and resource: 'WHOIS lookup for a domain or IP address, returning registration and ownership information.' This clearly distinguishes it from sibling tools like nslookup or reverse_ip, which serve different DNS/reverse-lookup purposes.

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 gives clear context about when to use the tool: for WHOIS registration and ownership data, including special support for Korean domains, domestic IPs, and AS numbers. It does not explicitly name alternatives or exclusion cases, but the intended use is obvious from the WHOIS-specific wording.

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