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

With no annotations, the description carries the full burden of disclosing behavior. It does state a non-obvious trait: no browser is launched. But it does not explain what 'can be opened' means operationally, whether a network request is made, how errors are handled, or what happens to the various input parameters. This is too thin for a tool with no annotation support.

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 short, front-loaded with the core action, and contains no filler. The second sentence earns its place by preempting a likely assumption about launching a browser. It sacrifices depth for brevity, but as a concise statement it is well structured.

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?

For a tool with nine parameters, no annotations, no output schema, and many closely related siblings, this description is incomplete. It does not explain expected inputs, return values, side effects beyond not launching a browser, or how it relates to web-fetch and playwright-url-ok. An agent cannot confidently select and invoke this tool correctly from the description alone.

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 all nine parameters. The tool description adds no parameter-level meaning beyond that. It also does not clarify which parameters are relevant to the URL check versus those that appear discarded, leaving the agent to rely on the schema descriptions 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 verb and resource: 'Check whether a URL can be opened.' The clarifying second sentence, 'No browser is launched,' helps distinguish it from browser-based tools like playwright-url-ok. However, it does not fully differentiate it from other URL-related siblings such as web-fetch, fetch-status, or normalize-url.

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?

There is no explicit guidance on when to use this tool instead of alternatives. 'No browser is launched' gives one exclusionary clue, but the description never mentions conditions, comparison to siblings, or scenarios where this check is preferred. Given the large sibling set, an agent would have to infer usage from the name alone.

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