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

With no annotations provided, the description bears the full burden of behavioral disclosure. It does mention that WHOIS/ownership data is not returned, which is a useful negative constraint, but it fails to disclose the behavior for the other 8 parameters and offers no clarity on error handling, side effects, or what exactly is returned beyond the split labels. The schema descriptions of 'discarded after the check' appear only in structured data, not in the description.

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, well-formed sentence that states the core action and a key business rule ('without WHOIS or ownership data'). It maximizes information per word and places the primary function upfront. No fluff or redundant phrases appear.

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 output schema, and no annotations, yet the description only covers one aspect (hostname splitting). An agent cannot determine how to use the tool for JSON validation, URL normalization, or file path checking, nor whether those parameters are mutually exclusive or complementary. The description is fundamentally incomplete for this complex, multi-parameter tool.

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 input schema thoroughly documents each parameter (e.g., 'HTTPS URL to normalize or cite'). The description only references 'hostname' and doesn't explain how the additional parameters interact with the split operation or whether they are alternate inputs or ignored. Since the schema covers all parameters, the baseline 3 is appropriate and the description adds no extra parameter meaning.

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 clear operation: 'Split a hostname into labels' and adds a useful constraint ('without WHOIS or ownership data'). However, the input schema exposes nine parameters (json, city, zone, etc.) that are not reflected in the description, creating a mismatch between advertised purpose and the full scope implied by the schema. An agent could still pick it for a hostname-splitting task, but the description doesn't distinguish it from siblings like normalize-url or url handling tools.

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 description says what it does but never states situations like 'use when you need to split a hostname' or 'do not use for full URL validation'. An agent is left to infer appropriateness from the name and one-line description, with no exclusions or prerequisites mentioned.

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