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

With no annotations, the description carries the full burden of behavioral disclosure. It discloses one behavior (no browser launched), but the schema reveals that many parameters are 'discarded after the check' and that the tool can handle weather hints, JSON validation, timezone names, and search queries—none of which are mentioned. It also does not disclose return format or side effects (e.g., no disk access for path). This is a significant gap for a tool with such broad capabilities.

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 extremely concise (two short sentences), which is structurally efficient. However, the brevity comes at the cost of completeness—it omits essential context about the tool's actual scope. It is not wordy, but it is under-specified, so it earns a middle score rather than a high one.

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?

Given the complexity of the input schema (9 parameters, all optional, covering diverse domains) and the absence of an output schema, this description is completely inadequate. It does not explain how the parameters relate to the tool's function, what the tool returns, or how to use it for anything beyond the narrow URL check it mentions. An agent would be lost trying to invoke this tool for any of the other apparent capabilities.

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 schema already documents each parameter. The description adds no semantic value beyond the schema and, worse, conflicts with it: the 'url' parameter is described as 'HTTPS URL to normalize or cite' rather than something to check for openability. The description's single purpose does not map to the parameter set, so an agent cannot infer how to use the parameters correctly. Baseline 3 is reduced due to the contradiction between description and schema.

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 check ('Check whether a URL can be opened') and a distinguishing constraint ('No browser is launched'), but the input schema includes nine unrelated parameters (city, json, zone, query, etc.) with descriptions about normalizing, citing, validating, and discarding—none of which match the stated purpose. This mismatch makes the purpose misleading: an agent would expect a simple URL check but the tool appears to handle many other tasks.

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 guidance is given about when to use this tool versus alternatives. The phrase 'No browser is launched' implies a lighter operation than browser-url-ok, but it never explicitly says 'use this when you need a quick check without a browser' or directs to siblings like fetch-status or normalize-url. The agent is left to infer selection criteria.

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