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 mentions that no browser is launched, but does not clarify what 'opened' means (e.g., HTTP request, DNS check, reachability), whether network calls are made, or any side effects. It also omits that many parameters are 'discarded after the shape check,' a detail only present in the schema descriptions.

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 with no filler or repetition. It is front-loaded with the primary action, making it easy to scan. However, the brevity is excessive for a tool with 9 parameters and many siblings, omitting critical context. Still, from a pure conciseness standpoint, it is efficient.

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 no annotations, no output schema, and a complex input schema of 9 parameters, this description is severely incomplete. It does not explain the return value, success/failure indicators, how different input types are handled, or any error conditions. An agent cannot reliably decide to use this tool based on the description alone, especially given the numerous sibling tools.

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?

The schema has 100% description coverage for all 9 parameters, each with a clear explanation of purpose and side effects (e.g., 'discarded after the shape check'). Since the schema fully documents parameters, the description does not need to add more. The baseline of 3 is appropriate because the description adds no extra parameter-specific meaning but the schema compensates.

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 ('check whether a URL can be opened') and differentiates from a sibling by noting 'no browser is launched.' However, it fails to mention that the tool accepts many unrelated input types (city, json, path, zone, query, etc.), making the actual scope ambiguous. An agent might misuse it for non-URL checks based on the narrow wording.

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 only guidance is the negative statement 'No browser is launched,' which hints at not using it when browser interaction is required but provides no explicit 'when to use' or 'when not to use.' It does not mention alternatives like browser-url-ok, validate-json, geo-hint, or other siblings that handle specific input types, leaving the agent to infer usage conditions.

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