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

Annotations already declare readOnlyHint, idempotentHint and openWorldHint, so safety is covered; the description still adds meaningful context beyond that: nothing is stored, the request is made as an anonymous visitor, an access pass is required and its price, and how to interpret the DNS result ('part of the visitors cannot reach the site'). It does not cover failure modes, timeouts, or whether results are cached.

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?

Front-loaded with the action and the returned data in the first sentence, then the exclusion, then cost/auth, then docs. It is dense but every clause carries information. The enumerated header list makes the first sentence long and slightly run-on, which is the only structural blemish.

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?

There is no output schema, and the description compensates by enumerating the return payload field by field (certificate validity/expiry/host coverage/protocol, redirect, named headers, mixed content, DNS filtering), plus the auth requirement and doc link. An agent has everything needed to decide and call 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% — both url and access_key are documented in the schema itself, including the max-length and the pass_ format. The description adds only that the page is read 'as a visitor', i.e. the url is treated as a public site address; it adds nothing about the access_key parameter beyond what the schema already says. Baseline 3 applies.

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 verb (reads as a visitor) and resource (public home page) and enumerates exactly what is returned: certificate fields, http→https redirection, named security headers, mixed content, and DNS-filter blocking. It explicitly carves out what it is not (malware scanning) and names the tools that do that, so it is distinguishable from deeper-analysis 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?

It gives an explicit exclusion — 'does not look for malware: that is the Express Analysis or Record' — which routes the agent away from this tool for that goal. It also states the prerequisite (access pass purchase). It lacks a positive 'use this first when…' framing and does not reference the listed sibling get_security_offer, so the routing picture is not fully closed.

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