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

With no annotations, the description carries the full burden. It discloses that it does not perform WHOIS/ownership lookups, which is a meaningful behavioral trait. However, it says nothing about side effects, network usage, or return format. Given the tool is likely a pure parse function, the lack of explicit 'read-only' or 'no side effects' is a minor gap, but the description still adds some value beyond the schema.

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 that front-loads the primary action and constraint. There is no redundancy or filler; every word earns its place. It is concise without being under-specified.

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 description is severely incomplete for a tool with 9 diverse optional parameters (ref, url, city, feed, json, path, zone, query) and no output schema. It only addresses the 'host' parameter, leaving the purpose of the other eight entirely unexplained. An agent cannot infer when to pass a 'city' or 'zone' or 'json' to this tool. The lack of an output schema also means the description should explain what the tool returns, which it does not. This is a major gap.

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 schema has 100% description coverage, so each of the 9 parameters is documented. The tool description adds no additional semantics beyond the schema—it only mentions 'hostname', which maps to the 'host' parameter. Since the schema already covers the parameters, the baseline of 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 clearly states the action ('Split') and the resource ('hostname') and explicitly excludes WHOIS/ownership data, which differentiates it from tools that might fetch such info. However, it does not name a specific sibling, so it misses the highest tier of clarity. The phrase 'without WHOIS or ownership data' is a useful negative constraint.

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 the many siblings (e.g., normalize-url, figma-url-shape, github-repo-shape). The only hint is the negative 'without WHOIS or ownership data', which implies it is not for ownership lookups, but it does not explicitly name alternatives or provide criteria for selection.

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