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

With no annotations, the description carries the full burden of behavioral disclosure. It states 'without WHOIS or ownership data', which implies a safe, non-network operation, but it does not disclose output format, side effects, error behavior, or that most parameters are discarded after a check. The one behavioral hint is useful but insufficient for a tool with 9 parameters and no output 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 sentence with no redundant words, but it is so terse that it omits critical context. It is concise but not well-structured; it front-loads the action but leaves the reader with more questions than answers about the tool's multi-input nature.

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, no output schema, and no annotations, this description is critically incomplete. It fails to explain how the tool handles each parameter, what 'labels' means in the output, or how the tool relates to its siblings. An agent would be unable to call this tool correctly based on the description alone.

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 baseline is 3, but the tool description adds no extra meaning to the parameters. It only references a 'hostname', which corresponds to 'host' but not clearly, and does not explain how the other 8 parameters (ref, url, city, feed, json, path, zone, query) relate to the described operation. In fact, the narrow description contradicts the wide parameter set, failing to help an agent choose the right parameter.

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 'Split a hostname into labels', which is a specific verb and resource, but it only mentions hostname while the input schema accepts 9 unrelated parameters (ref, url, city, feed, json, path, zone, query). This suggests the tool is not solely about hostnames, so the description is misleading about the tool's actual scope and does not clearly distinguish it from sibling shape tools like figma-url-shape or jira-key-shape.

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 is provided on when to use this tool versus alternatives. There is no mention of conditions, exclusions, or which sibling tools are more appropriate for specific scenarios. The agent is left to infer usage from the bare description and schema.

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