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

Adds one behavioral detail beyond the annotations: 'No browser is launched.' This usefully sets expectations about cost and side effects. Still, it does not explain what 'can be opened' actually means (syntactic validation vs. HTTP request), and it omits whether inputs are discarded. With annotations already covering readOnly/idempotence, the description adds only modest behavioral clarity.

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?

Two short, front-loaded sentences with zero padding. The core action and the key differentiating behavior ('No browser is launched') are both present, so it is efficient and to the point.

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 8 parameters and no output schema, a one-sentence description is inadequate. It does not explain the relationship between 'url' and the other schema fields (city, feed, json, path), does not describe the return value or response format, and leaves agents unsure how to interpret the result of the 'check.' This is a significant completeness gap.

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 tool description itself does not mention parameters, but the input schema already provides descriptions for all parameters with high coverage, so the baseline is met. The description adds no extra meaning about parameter purposes or relationships; in fact, it emphasizes only 'url,' which could mislead given the schema's diverse fields.

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?

States a clear action and resource: 'Check whether a URL can be opened.' The qualifier 'No browser is launched' helps distinguish it from heavier browser-based alternatives like browser-url-ok. However, the schema contains many unrelated parameters (city, feed, json, path), which muddies the actual scope and prevents a perfect score.

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 when-to-use guidance is provided. It does not mention when to choose this tool over siblings like browser-url-ok, web-fetch, or fetch-status, nor any exclusions or prerequisite conditions. The agent is left to infer usage entirely.

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