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

Beyond the readOnlyHint and openWorldHint annotations, the description discloses the exact diagnostic areas checked, the verdict model (problems, warnings, good), the inclusion of findings and remediation guidance, and an important limitation around DKIM checks at common selectors. This gives an agent substantial behavioral context for invoking the tool correctly.

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 definition is front-loaded with the core purpose and the scope list is justified by the breadth of checks performed. It is a dense single paragraph with heavy parenthetical enumeration, which slightly reduces readability despite containing little obvious waste.

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 read-only diagnostic with no output schema, the description is complete enough: it explains the checks, the verdict format, finding details, remediation guidance, and representative user questions. No critical invocation detail appears to be missing.

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 input schema has 100% description coverage for the single required domain parameter, so the schema already explains the expected value. The description does not add format, validation, or normalization details beyond that baseline.

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 makes the tool’s purpose highly specific: it reports a domain’s security posture across email authentication, DNSSEC, CAA, HTTPS/HSTS, certificate status, registration expiry, and security.txt. The enumerated checks distinguish it from generic sibling checks such as site_check or dev_check, and the example queries reinforce the exact use case.

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 clear usage contexts: launching or running a site, checking a vendor, and answering questions like whether email can be spoofed or when a certificate expires. It does not explicitly state when not to use it or name an alternative sibling, so it falls short of the highest guidance level.

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