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

No annotations are provided, so the description carries the full burden of behavioral disclosure. It discloses that the tool performs deterministic checks, does not load page content, blocks localhost/private addresses, optionally queries Google Web Risk, and incurs a cost. It also notes that no LLM is used and that a clean result is not a guarantee. This is comprehensive behavioral transparency for a tool of this complexity, though it could mention error handling or response format.

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 concise, with every sentence adding value: cost, use case, safety features, optional integrations, and limitation. It is front-loaded with the most critical information (cost and when to use). No fluff or repetition.

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 tool has a single parameter and no output schema, so the description covers the essential usage context (when, what, how). It explains the tool's internal checks, cost, and limitations. Minor gaps include the exact return structure (though not necessary given no output schema) and potential error conditions, but for this simple tool, the description is complete enough.

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 0% coverage and only one parameter, 'url'. The description explains what the tool does with the URL, implying that the 'url' parameter should be the URL to check. It also gives context on the URL length (max 4096) implicitly through schema. The description adds meaning beyond the type definition by clarifying the tool's behavior on the URL, which is sufficient for a single parameter.

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 clearly states the tool's purpose: to perform a preflight URL check before opening or trusting a URL. It mentions specific actions (checks redirects, blocks localhost, optionally queries Google Web Risk) and distinguishes it from general URL utilities. It also notes the cost and no-LLM nature, which is unique among siblings.

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 explicitly states when to use this tool: 'Call before an agent opens, follows, downloads from, or trusts an unknown URL.' It also provides a clear exclusion—'A clean result is not a guarantee of safety'—which sets expectations. While it doesn't mention alternatives, the sibling tools are all invoice-related, so the usage context is clear that this is the only URL check tool, making the guidance sufficient.

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