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

With no annotations provided, the description carries the full burden and does meaningful work: it discloses the per-check price (€0.0005), that billing is tied to the Bearer API key, and that no server-side scheduling occurs. It leaves out failure/timeout behavior and any rate limits, so it is strong but not complete.

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?

Four short sentences, front-loaded with output content, then operational constraints, then the parameter. Every sentence contributes distinct information and nothing is repeated from structured fields.

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?

An output schema exists, so return values need not be re-explained, yet the description still summarizes them usefully alongside cost, auth and invocation cadence. For a single-parameter probe the only real gap is error/timeout behavior.

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 coverage is 0% and the schema only offers an untyped string/null, so the description's "url: site url or host" adds genuine meaning by permitting a bare hostname rather than a full URL. It does not clarify what happens if the optional url is omitted (default null), which keeps it below a 5.

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 names a specific resource-and-output set: HTTP status, latency, redirects, server header, TLS issuer and days to expiry, so an agent knows exactly what a call yields. It does not distinguish the tool from the nearest sibling, domain_health, which prevents a top score.

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?

"One probe per call; schedule them from your side" tells the agent this is a single-shot primitive rather than a monitor, which is real usage guidance. However, it never states when to prefer this over domain_health or link_preview, nor any prerequisites or exclusions.

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