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

Annotations are absent, so the description must disclose behavior. It only states 'without WHOIS or ownership data' and the core action, but says nothing about side effects, permissions, error cases, or what 'shape check' means for the varied parameters. The schema hints at discarding some inputs, but the description doesn't clarify.

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 short sentence, which is concise, but it under-specifies the tool's full capability. Important context (multi-parameter nature, return behavior) is absent, and the sentence doesn't front-load any operational guidance.

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 9 parameters, no output schema, and no annotations, the description is severely incomplete. It covers only a narrow interpretation (splitting hostnames) while ignoring most of the tool's apparent surface area, leaving the agent unable to correctly invoke it for non-hostname 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% with per-parameter descriptions, so the baseline is 3. However, the description fails to explain how most parameters (city, feed, json, zone, query) relate to splitting a hostname, making their semantics confusing. The description adds no extra meaning and even conflicts with the schema's breadth.

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 says 'Split a hostname into labels', which is a specific verb and resource, but the input schema lists 9 unrelated parameters (ref, url, city, feed, json, path, zone, query) that do not all relate to splitting a hostname. This mismatch makes the actual purpose unclear and fails to 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?

The description gives no guidance on when to use this tool versus alternatives. With many sibling shape-check tools (e.g., github-repo-shape, jira-key-shape), the lack of any selection criteria or exclusion conditions leaves the agent guessing.

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