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

Annotations already declare readOnlyHint, idempotentHint, openWorldHint, and destructiveHint=false, so the safety profile is fully covered structurally. The description adds the shape of the returned data, but says nothing about pagination, result caps, rate limits, or whether lookup requires a live scan – with annotations carrying the safety burden, a 3 is appropriate.

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?

Two compact sentences, front-loaded with what is listed and followed by the payoff of using it; no filler. Slightly over-brief given the unaddressed operational details.

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?

An output schema exists, so return values need not be explained, and the tool is a read-only single-parameter listing operation. The description covers the essentials; only operational details like result limits and pagination are absent, which is a minor gap.

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?

There is a single required 'domain' parameter with 0% schema description coverage. The description implicitly clarifies it by saying 'subdomains of a domain', but adds no syntax, format, or scope guidance (e.g., apex vs subdomain, wildcard handling) beyond 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?

The description gives a specific verb ('List') and resource ('subdomains of a domain found through Certificate Transparency'), plus the payload contents (DNS record type, IPs, TTL, seen dates). It is clear what the tool does, but it never names or distinguishes itself from close siblings like get_ct_certificates, get_ct_domains_by_ip, or get_ct_similar_domains.

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 closing sentence 'Useful for finding the other hosts of a domain' implies the use case, but there is no explicit when-to-use, when-not-to-use, or pointer to an alternative CT tool. The agent must infer the boundary against sibling tools on its own.

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