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

With no annotations, the description must carry the full burden of behavioral disclosure. It adds one useful note ('No browser is launched') but doesn't explain side effects, whether the check is read-only, what it actually does beyond a vague 'opened,' or how results are returned. The single sentence leaves most behavioral traits undisclosed.

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 short and front-loaded, which is positive, but it is under-specified. It does not waste words, yet it lacks essential information, so it's not appropriately sized for a tool with 9 parameters and no output schema. It is concise but not sufficiently informative.

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?

This is a 9-parameter tool with no annotations and no output schema. The description provides only a one-line purpose and a single behavioral note. It does not explain what 'opened' means, how parameters are used (they seem unrelated), what the return value is, or any constraints. It is severely incomplete for an agent to call it correctly.

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, but the description adds nothing about parameters. Moreover, the parameters (ref, city, feed, host, json, path, zone, query) seem unrelated to the stated purpose of checking a URL, and their descriptions (e.g., 'discarded after the shape check') imply they are placeholders. The tool description does not reconcile this mismatch, so it fails to add meaning beyond 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 verb and resource: 'Check whether a URL can be opened.' It also adds a behavioral differentiator, 'No browser is launched,' which hints at a distinction from browser-launching tools like browser-url-ok. However, it doesn't explicitly name the sibling or elaborate on what 'opened' means, so it's clear but not fully distinguishing.

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 offers no guidance on when to use this tool versus alternatives like fetch-status, browser-url-ok, or normalize-url. It only states what it does, not when to choose it, nor any exclusions or prerequisites.

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