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

With no annotations provided, the description carries the full burden of explaining behavior. It only discloses a negative feature ('No browser is launched') without clarifying what the check actually does—network request, syntax check, or something else. The schema reveals many parameters (ref, city, json, etc.) with notes like 'discarded after the shape check,' but the description is silent on how these relate to the operation, making the tool's behavior opaque.

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 action and includes a helpful clarification. There is no fluff or redundancy. However, it omits essential detail, so while it is well-structured for its length, it trades completeness for brevity.

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 tool has 9 parameters, no annotations, and no output schema, the description is grossly insufficient. It fails to explain how the parameters are used, what the tool returns, or what 'can be opened' means operationally. The presence of apparently irrelevant parameters (city, zone, query) that are 'discarded' further confuses the agent, leaving it without a clear mental model of the tool's function.

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 coverage is 100%, meaning every parameter already has a description in the input schema. The tool description adds no extra meaning to any parameter, so it meets the baseline for high coverage. It does not compensate for the ambiguity of the overall behavior, but parameter-level semantics are adequately handled by the 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 clear action ('check whether a URL can be opened') and adds a behavioral note (no browser launched). It is specific enough to distinguish it from tools like normalize-url that focus on normalization, but the phrase 'can be opened' is ambiguous—does it imply an HTTP request, syntax validation, or something else? No explicit differentiation from siblings is provided, but the core purpose is identifiable.

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 or when to prefer an alternative. It does not mention conditions under which this tool is appropriate, nor does it reference any sibling tools. An agent receives no hint about how to choose this over domain-shape, fetch-status, or normalize-url, leaving usage entirely to inference.

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