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

Annotations already declare read-only, idempotent, open-world, non-destructive behavior, so the safety profile is covered. The description adds genuinely new information beyond that: a per-call cost of 1 credit and the shape of the returned data (status, server, HSTS headers), which matters since there is no output schema. It does not say what is returned for a failed/non-HTTPS domain, keeping it below 5.

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?

One compact sentence plus a parenthetical cost note, with the core purpose front-loaded and zero filler. The phrasing is a noun fragment ('Whether a domain answers...') rather than a direct verb, which slightly weakens immediacy but does not waste space.

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 simple one-parameter read tool with no output schema, the description covers purpose, returned fields, and cost, which is enough to call it correctly. It omits edge-case behavior such as non-HTTPS responses, redirects, or timeouts.

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?

With a single parameter and full schema coverage, the schema is the primary reference, so a 3 baseline applies. The description does confirm the parameter is a domain name and implies the check target, but adds no format or validation guidance beyond that.

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?

States a specific action and resource: checking whether a domain answers over HTTPS, and names the returned data (status, server, HSTS headers). This clearly separates it from siblings like rdap_lookup or unshorten, though it never explicitly contrasts with them.

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?

There is no guidance on when to use this versus alternatives, nor any prerequisites or exclusions. The only contextual hint is the credit cost, which is a budget note rather than a use-case rule.

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