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 does disclose that no browser is launched, which is useful, but it fails to explain how 'can be opened' is determined, whether a network request is made, whether inputs are discarded, or what side effects might occur. The schema's repeated 'discarded after the check' hints at important behavior that the description omits.

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 compact and front-loaded: the main function appears first, followed by a key behavioral qualification. Both sentences earn their place, and there is no wordy filler. It loses one point because it is so minimal that it under-specifies the tool's broader parameter surface.

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 9 optional parameters, no annotations, and no output schema, this one-sentence description is not enough for an agent to understand how to invoke the tool correctly. It does not state what the tool returns, how multiple parameters interact, or which parameter is relevant for the stated URL-checking purpose. The rich schema descriptions mitigate but do not compensate for the missing overall behavioral context.

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 baseline is 3 even without parameter details in the tool description. The description adds no parameter-level meaning; it only mentions 'URL' while the schema documents many unrelated optional parameters. Since the schema already explains each parameter, a 3 is appropriate.

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 gives a clear verb and resource: 'Check whether a URL can be opened.' However, the input schema contains 9 parameters that are not URL-only (git ref, city, RSS feed, JSON, timezone, query), so the stated purpose does not match the actual breadth of the tool. It also does not differentiate this tool from closely related siblings like normalize-url, fetch-status, or playwright-url-ok beyond saying no browser is launched.

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 provided about when to choose this tool over alternatives. The only contextual hint, 'No browser is launched,' implies a use case where browser side effects should be avoided, but the description never states exclusions, alternatives, or conditions such as 'use fetch-status for live HTTP checks' or 'use playwright-url-ok when browser rendering is needed.'

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