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

With no annotations, the description carries full burden. It fails to disclose that most parameters are discarded after the check, that no disk access occurs, or any return format. It only mentions the absence of WHOIS data, which is minor.

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?

It is a single sentence, so concise, but it is under-specified and does not front-load the actual broad purpose. The brevity sacrifices necessary information.

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 tool with 9 parameters and no output schema, this description is grossly incomplete. It omits what happens with all other parameter types, any return values, and the general utility. It only describes a narrow subset.

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 descriptions cover 100% of parameters, each clearly explaining its role and discarding behavior. The tool description adds no additional meaning about parameters, so baseline 3 applies.

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 action 'split a hostname into labels' but the tool has 9 parameters covering URL, JSON, timezone, path, etc., so it is misleading about the tool's actual scope. It does not convey that this is a general shape checker across many input types.

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?

No guidance on when to use this tool versus siblings like normalize-url, validate-json, or geo-hint. The only hint is 'without WHOIS or ownership data', which implicitly excludes some tools but does not name alternatives or conditions.

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