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

With no annotations provided, the description carries the full behavioral disclosure burden. It discloses that the call is cheap, does not download the page, costs $0.005 USDC, and that header presence is a hygiene signal, not a safety verdict. This adds meaningful operational and interpretive context beyond the bare schema.

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 three sentences with no filler. It front-loads the return contents, then gives usage context, then adds the important caveat and cost. Every sentence contributes decision-relevant information.

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 single-parameter tool with no output schema, the description is remarkably complete: it lists what data will be returned, when to use it, what it does not tell you, and what it costs. An agent has enough information to invoke it correctly and interpret results appropriately.

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 already fully documents the single url parameter with 100% coverage, so the baseline is 3. The description adds no additional format detail or constraints about the URL beyond what the schema states, which is acceptable for a single, self-explanatory 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 specifies exactly what the tool returns: response status, server software, content type, caching, and the six standard security headers. It also clearly separates this from sibling tools by positioning it as a lightweight, non-downloading host profiling check rather than a page fetch or URL resolution.

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 provides explicit use cases: checking whether a URL is live and well-formed before relying on it, and cheaply profiling a site without downloading it. It does not name sibling alternatives or state when not to use it, but the context is clear enough for an agent to select it appropriately.

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