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

With no annotations, the description must fully disclose behavior. It only mentions hostname splitting, but the schema reveals the tool accepts many other input types (ref, url, city, feed, json, path, zone, query) and discards them after checks. The description is misleading about the tool's actual scope, failing to disclose that it validates various data shapes beyond hostnames. No error handling, output format, or side effects are mentioned.

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 sentence that front-loads the core action. It is concise with no fluff, but it omits critical scope information, which is a completeness issue rather than a structure issue. For conciseness alone, it is well-structured.

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?

This tool has 9 parameters, no annotations, and no output schema, so the description must be thorough. A one-line statement covering only hostname splitting while ignoring the other 8 input types is completely inadequate for an agent to understand when and how to invoke the tool. It fails to mention return values, error behavior, or intended use cases for the other parameters.

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 coverage is 100%, so the baseline is 3. The description adds no parameter-specific semantics beyond what the schema already provides; it only references hostname, while other parameters like city or json are not explained in the description. The description does not compensate for the gap or add value beyond the schema.

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 verb 'Split' and the resource 'hostname', and explicitly excludes WHOIS/ownership data, which distinguishes it from related tools like figma-url-shape or github-repo-shape. The scope is unambiguous.

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 description implies usage (for extracting labels from hostnames) but does not explicitly state when to use this tool versus alternatives, nor does it provide any exclusion criteria. There is no mention of when not to use it, so the guidance is only implied.

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