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

No annotations are provided, so the description carries the behavioral burden. It does disclose a meaningful trait: no WHOIS/ownership lookup and a local split operation. However, it does not describe the return format, error behavior, or whether any network or DNS validation occurs, leaving clear gaps.

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 one front-loaded sentence with no filler, and the WHOIS qualifier earns its place. It is concise, though perhaps too sparse to serve as a complete definition for a tool with a seven-parameter schema.

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?

With no annotations and no output schema, the description needs to supply more usage and return context, but it only gives the core split action and a negative qualifier. The schema's extra parameters (ref, url, city, feed, json, path) are not reconciled with the hostname-only description, and no alternatives or output format are mentioned.

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?

The input schema has 100% per-parameter descriptions, so the baseline is 3 even though the description adds no parameter detail. The description's 'hostname' maps naturally to the `host` parameter, but the tool description does not clarify which of the seven parameters apply or whether they are mutually exclusive.

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'), and the 'without WHOIS or ownership data' qualifier narrows it to syntactic label extraction. It does not explicitly distinguish among the sibling shape tools, and the schema's many unrelated fields (ref, city, json, path) create some ambiguity, but the sentence itself is clear.

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?

The only usage hint is the negative qualifier 'without WHOIS or ownership data,' which tells the agent what not to expect. There is no explicit when-to-use guidance, no named alternative, and no mention of how this tool relates to siblings like normalize-url, web-fetch, or browser-url-ok.

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