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

With no annotations, the description must disclose behavior, but it only mentions HEAD on a URL. The schema hints at a broader role (e.g., 'discarded after the shape check', 'no disk access') that the description completely ignores. It fails to reveal that most parameters are discarded or that the tool likely returns a status indicator for many input types, not just HTTP status.

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, which is concise and front-loaded, but it's under-specified. It lacks structure and doesn't provide any context beyond the action. It's not overly verbose, but it's too sparse to be effective.

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 nine parameters, no output schema, and no annotations, the description is drastically incomplete. It doesn't explain the return format, the meaning of 'status', or how to choose among the many input types. An agent cannot correctly invoke this tool 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?

The schema provides 100% coverage of all nine parameters, each with a description (e.g., 'discarded after the shape check'). The tool description adds no extra meaning and actually narrows the scope to URL-only, which could confuse agents. Since the schema is complete, the baseline of 3 applies, but the description doesn't enhance parameter understanding.

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 and resource ('HEAD a public URL') but the schema reveals nine diverse parameters (url, json, path, zone, query, etc.), suggesting the tool actually handles many input types, not just URLs. This mismatch makes the purpose ambiguous and potentially misleading—an agent might think it's URL-only when it appears to be a generic shape/status checker.

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 its many siblings (browser-url-ok, web-fetch, normalize-url, validate-json, etc.). It doesn't mention exclusions or alternatives, leaving the agent to infer usage from the vague 'HEAD a public URL' statement.

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