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

The description discloses that it uses the HEAD method and returns only the status, which is a behavioral trait. However, it doesn't mention the other capabilities hinted by the schema (e.g., validating JSON, checking timezone names). With no annotations, the description carries the full burden, but it only covers one use case. This partial transparency could mislead the agent into thinking the tool is only for URLs.

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 concise sentence that immediately states the action and output. It's well-structured and front-loaded with the key information. No waste.

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 tool has 9 parameters, no annotations, and no output schema. The description only addresses one use case (URL HEAD check) and ignores the other parameters entirely. This is inadequate for an agent to understand the full scope or how to use the tool for non-URL inputs. The lack of output format details also contributes to incompleteness.

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 descriptions for all 9 parameters (100% coverage), so the description doesn't need to add parameter meaning. However, the description doesn't clarify which parameter is primary or how the others are used. Since the schema covers all parameters, a baseline of 3 is appropriate.

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 action: 'HEAD a public URL and return status only.' This clearly identifies the tool as a lightweight HTTP status checker. However, it doesn't distinguish from similar tools like browser-url-ok or playwright-url-ok, which also check URLs, so the differentiation is limited. The presence of many unrelated parameters in the schema (ref, city, json, etc.) is not addressed, which slightly muddies the purpose.

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 provides no guidance on when to use this tool versus alternatives. It doesn't mention that this is a quick HEAD check vs a full page load check, nor does it reference any sibling tools. The agent is left without criteria for tool selection.

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