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

With no annotations, the description carries the full burden and does so well: it discloses no API key/account required, a concrete price ($0.005 per call) and the payment rail (x402/USDC), and clarifies the read-only nature and data source (CT logs, historical issuance rather than live serving). It even compensates for the absent output schema by enumerating the returned fields.

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 a 'Use when...' trigger, then the crucial scope clarification, then commercial/access facts — a sensible ordering. It is dense but nearly every clause adds information; the parenthetical field list is the only slightly heavy element.

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 two-parameter, no-annotation, no-output-schema lookup tool this is close to complete: trigger, data source, scope boundary, returned fields, access requirements and price are all present. Remaining gaps are minor operational details — rate limits, behavior on very large domains, and error semantics.

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%, so both parameters are already self-documenting; the baseline of 3 applies. The description adds conceptual value ("every hostname each certificate covers") that frames what the subdomains flag affects, but it does not explain the domain param's URL/email normalization — that detail lives only in the schema.

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 and resource — audit every currently valid publicly issued certificate for a domain, read from Certificate Transparency logs — and enumerates the fields returned (issuer, validity window, expiry, revocation, hostnames). It also draws the key conceptual line, 'reports what was ISSUED ... not what the server is serving today', which separates it from live-TLS-style siblings like red_domain_check.

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?

"Use when an agent must audit what certificates exist for a domain" gives a clear triggering context, and the follow-on sentence sharpens it into a concrete use case (finding certificates you did not know existed). It stops short of naming an alternative sibling or an explicit when-not-to-use case, so it is a strong 4 rather than a 5.

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