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

The readOnlyHint annotation already indicates a safe read operation, and the description adds beyond that: the scope constraint that subdomains are not tracked, and the cost signal of 100 points per call. It does not describe the exact return shape, but for a simple read-only lookup with annotations present, the added context is meaningful.

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 main purpose. The Korean sentence largely repeats the English sentence, which is mild redundancy, but the scope caveat and cost note are valuable additions. It is appropriately sized overall, with only one repetitive sentence keeping it from a top score.

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, read-only lookup with no output schema and no nested objects, the description covers the essential context: what the tool does, the domain scope, and the cost. It does not specify the output format in detail, but 'historical IP address changes' sufficiently conveys what the agent should expect.

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 documents the single 'domain' parameter at 100% coverage with an example. The description adds important semantic nuance not in the schema: the query is based on the top-level domain and subdomains are not tracked, which tells the agent to provide an apex domain like 'apick.app' rather than a subdomain.

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 opens with a specific verb and resource: 'Look up the historical IP address changes of a domain.' This clearly distinguishes the tool from siblings like nslookup (current DNS), reverse_ip (IP-to-domain), and whois (registration info), since it is specifically about historical IP changes. The Korean sentence reinforces the same purpose without ambiguity.

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 intended use is clear: use it when you need historical IP changes for a domain. The description also gives an explicit exclusion: subdomains are not tracked and lookup is based on the top-level/apex domain. It does not explicitly name alternative tools for other lookups, but the historical vs. current distinction is implied well enough.

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