Reverse DNS lookup

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

Annotations already declare readOnlyHint=true, which tells the agent this is a safe read operation. The description adds no extra behavioral context such as output format, rate limits, or error conditions. The phrase 'associated hostnames' is the only addition, but that is already implicit in the schema and title, so it adds little value.

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 a single, focused sentence with no fluff or irrelevant details. It is front-loaded with the action and resource, making it easy to parse quickly.

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 1-parameter tool with annotations, the description is adequate but not thorough. There is no output schema, so the description could have clarified the return format (e.g., a mapping of IPs to hostnames) and could have mentioned that this is the reverse counterpart to shodan_dns_resolve. Given its simplicity, the description is minimally complete but leaves room for improvement.

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% (the single 'ips' parameter has a clear description). The tool description adds no further meaning beyond what the schema provides, only restating that it handles one or more IPs. Baseline 3 is appropriate since the schema does the heavy lifting.

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 reverse DNS lookup, using a specific verb ('look up') and resource ('hostnames associated with IP addresses'). It does not explicitly differentiate from the sibling tool shodan_dns_resolve (forward lookup), so it doesn't earn a 5, but the purpose is unambiguous.

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?

There is no guidance on when to use this tool versus alternatives. It does not mention that shodan_dns_resolve is the forward-lookup counterpart, nor any context like prerequisites or typical use cases. The description implies usage by stating the function, but siblings are not referenced.

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