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

With no annotations present, the description carries the full burden of behavioral disclosure. It reveals one trait—'No browser is launched'—but does not explain that several parameters are 'discarded after the shape check,' whether any network request occurs, or what 'can be opened' operationally means. This is insufficient transparency for a tool with multiple input types.

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 is front-loaded with the primary action and includes a useful qualifier. It contains no waste. However, its brevity borders on under-specification, omitting important context about the schema's breadth.

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 description covers only the URL aspect while the schema exposes seven parameters with varying purposes. There is no output schema and no annotations. An agent would be uncertain about what inputs to provide and what side effects occur. The tool appears more complex than the description acknowledges, leaving significant gaps.

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?

All parameters have descriptive text in the input schema, so the baseline is 3. The tool description adds no additional parameter-level meaning beyond the schema. While some schema descriptions (e.g., 'City name for a public weather hint') seem inconsistent with the stated URL-check purpose, that inconsistency is not addressed by the description.

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 and resource: 'Check whether a URL can be opened.' It also includes a distinguishing clause 'No browser is launched.' However, the input schema contains many parameters unrelated to a simple URL check (city, feed, json, path, ref), causing ambiguity about the tool's actual scope and 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 gives no explicit guidance on when to use this tool versus alternatives like browser-url-ok or web-fetch. The clause 'No browser is launched' implies a lightweight alternative, but the description does not state selection criteria, exclusions, or context where this tool should be preferred.

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