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

With no annotations, the description must carry the full burden of behavioral disclosure. It mentions 'No browser is launched' but does not state whether a network request is made, what side effects occur (e.g., caching, logging), or how the check is performed. The description is also inconsistent with the parameter list, which includes unrelated fields (city, feed, json, path, zone, query) that are not explained in the context of a URL check—this lacks transparency about the tool's actual scope.

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 front-loads the primary action and a key constraint. It contains no filler or redundancy. However, the brevity comes at the cost of missing important context, which is a trade-off but still earns a high score for efficiency.

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 is complex with 9 parameters, no annotations, and no output schema, yet the description provides minimal context. It fails to explain the tool's full behavior, the purpose of the diverse parameters, the expected output, or how it differs from many siblings. This is significantly incomplete for an agent to call it correctly.

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 parameters are individually documented. However, the tool description adds no additional meaning; it does not explain how these parameters relate to the stated URL check. The high schema coverage sets a baseline of 3, but the description fails to clarify the surprising mix of parameters, leaving the agent to infer their role from the schema alone.

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 ('Check whether a URL can be opened') and adds a distinguishing trait ('No browser is launched'), which differentiates it from browser-based alternatives like browser-url-ok. However, 'can be opened' is somewhat vague—it doesn't specify whether this involves an HTTP request or merely URL format validation, leaving some ambiguity.

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 a hint about when to use it (when you don't need a browser) but does not explicitly name alternatives or conditions. There is no clear guidance on when to choose this tool over siblings like web-fetch or fetch-status, nor any exclusions or prerequisites.

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