Subdomains from certificate logs

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

Adds genuine context beyond the annotations: named upstream providers, a fallback path when crt.sh is down, and the important caveat that returned hosts 'may no longer exist' (stale data). 'No key needed' clarifies auth requirements. Return format/pagination is not described, but annotations already cover safety and idempotency.

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 short sentences, zero filler, front-loaded with what the tool returns and backed by source and caveat. Every clause carries information.

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?

With no output schema the description should convey the return shape and the undisclosed investigation_id. It hints that results are hostname lists but leaves the second parameter entirely unexplained and says nothing about volume or paging of CT-log results.

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 0% for both parameters, so the description must compensate and does not. The sole required parameter 'domain' is only obliquely referenced ('under a domain'), and 'investigation_id' is never mentioned at all — the agent gets no idea what it does or when to supply it.

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 resource (hostnames under a domain that have had TLS certificates) and the exact data source (crt.sh / Cert Spotter), which is far more informative than the title alone. It does not explicitly distinguish itself from siblings like resolve_domain or shodan_search, but the certificate-transparency framing makes its niche reasonably clear.

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 it to find other hosts a domain runs' gives an implied when-to-use, but there are no exclusions and no named alternatives among the many sibling tools (resolve_domain, shodan_search, investigate_target). The agent must infer whether this is a discovery step or a validation step.

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