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

Annotations already declare readOnlyHint=true and openWorldHint=true, so the safety profile is covered. The description adds two useful behavioral details beyond annotations: calls cost 100 points each, and the input must be in IP-address format only. It still does not describe output size, pagination, or result freshness, which keeps it from a 5.

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 definition is short and front-loads the core operation, then adds the format constraint and cost. The English and Korean lines partly duplicate each other, but the overall length remains efficient and easy to parse.

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 read-only, one-parameter lookup, the description covers what the tool returns (domains hosted on the IP), the input restriction, and the per-call cost. Without an output schema, it could say a bit more about result shape or historical coverage, but it is otherwise sufficient to call 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?

Schema coverage is 100%, so the schema already defines the single ip parameter and gives an example. The description still adds a meaningful constraint by saying only IP-address format is accepted, which clarifies that hostnames or domains are not valid inputs.

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: reverse IP lookup that lists domains hosted on a given IP address. It is clear enough to separate from nslookup and whois by implication, but it does not explicitly distinguish itself from the nearby sibling ip_history, especially since the Korean text refers to domain history information.

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?

Use is implied by the operation name and the statement that only IP address format is allowed. However, there is no explicit guidance on when to choose reverse_ip over alternatives such as ip_history, nslookup, or whois, and no exclusions are stated.

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