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

With no annotations provided, the description carries the full burden. It does disclose a meaningful behavioral trait: the tool does not fetch WHOIS or ownership data. However, it does not mention output format, failure behavior, network access, or whether inputs are discarded, so transparency is only partial.

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, direct sentence with no filler. It front-loads the action and scoping constraint efficiently, making it 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?

The tool has 9 optional parameters, no annotations, and no output schema, yet the description only covers hostname splitting. It does not clarify which parameter to use, what the output looks like, or how it relates to the many sibling shape tools. The mismatch between the narrow description and the broad schema leaves important context missing.

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 description coverage is 100%, so the baseline is 3. The description adds no parameter-level meaning beyond the schema, and it fails to specify that the 'host' parameter is the intended input while the other parameters appear unrelated or are marked discarded. The schema itself provides clear descriptions, so the agent can still infer the likely parameter.

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 ('split') and resource ('hostname into labels'), and adds a clear exclusion ('without WHOIS or ownership data'). It is reasonably distinct from sibling tools like normalize-url and browser-url-ok, though it does not explicitly clarify that only the 'host' parameter is relevant despite the schema containing many unrelated fields.

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. The phrase 'without WHOIS or ownership data' hints at a use case, but no sibling tool or condition is named, and there is no 'use X instead when...' guidance for an agent to follow.

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