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

With no annotations, the description still implies read-only via 'Lists' and adds a cost disclosure (0.003 USDC per call via x402) that the schema does not carry, which is genuine behavioral value. However, it omits the 402 retry flow, rate limits, and any coverage caveats (e.g., whether subdomain results are capped by 'limit').

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, front-loaded with what is returned, followed by use case and pricing. No filler or redundant restatement of the name.

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?

No output schema and no annotations, so the description carries the burden — and it does describe the returned fields well (issuer, validity, days left, subdomains). The remaining gap is how 'limit' affects results and whether the 402 first-call behavior needs flagging beyond the schema text.

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 67%: 'domain' and the x402 'paymentProof' flow are documented in the schema, while 'limit' has only constraints (1-100, default 20) and no stated meaning. The description never mentions 'limit' or what it bounds (certificates vs. subdomains), so it adds nothing over 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?

Specific verb ('Lists') plus two precisely scoped resources: valid TLS certificates for a domain and subdomains found in Certificate Transparency logs. The mention of issuer/validity/days-left and CT logs cleanly separates it from siblings such as whois, dns_lookup, and domain_reputation.

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?

'Good for recon and expiry monitoring' implies usage but names no alternatives and gives no when-not-to-use conditions. An agent must infer that dns_lookup/whois are the wrong choices rather than being told.

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