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

With no annotations, the description carries the burden and does well: it discloses that the tool reads public logs only ('never touches the target'), that results are historical and may belong to a previous owner, and how to mitigate with `since`. It does not mention rate limits or latency for crt.sh, which would complete the picture.

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?

Three sentences, front-loaded with what the tool does and what it returns, followed by the key usage caveat. No filler; slightly dense but every sentence earns its place.

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 read-only enumeration tool with no output schema, the description is nearly complete: it explains data source, return contents, safety profile, and the historical caveat. Remaining gaps are minor operational details like result limits or rate 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 100%, so the schema already documents both parameters, including `since` with format and semantics. The description reinforces the rationale for `since` (registration date to exclude prior owners) but adds no syntax beyond what the schema states. Baseline 3 is appropriate.

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: enumerates subdomains and certificate-issuance history from CT logs (crt.sh), naming exactly what is returned (names, issuing CAs, issuance span). It is clearly distinguishable from siblings like tls_certificate or ct_org_search by its per-domain historical scope.

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?

The description gives strong context: use it to reveal names even behind a CDN without touching the target, and warns that CT is historical, advising use of `since` (registration date) to exclude a previous owner's names. It lacks an explicit named alternative or exclusion against siblings like ct_org_search, so it falls short of 5.

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