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

Goes well beyond the annotations: discloses the data source (CertSpotter with crt.sh fallback), the crucial behavioral caveat that results reflect the newest CT-log certificate rather than the served one, the additional https/HSTS probing, and the $0.002 USDC x402 payment model with failed calls uncharged. The readOnly/openWorld hints are complemented rather than repeated.

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-loads purpose and return fields in the first sentence, then the CT-log caveat, then pricing. Dense but efficient; every clause (source, caveat, price, limits) is actionable, with only mild redundancy against the output schema.

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 one-parameter lookup with an output schema and annotations, the description covers the non-obvious essentials: data provenance, the served-vs-issued mismatch, public-hostname restriction, and metered payment. An agent can decide to call it and anticipate what it gets without further reading.

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?

The schema already documents the single hosts parameter as comma-separated public hostnames, 1 to 10 (100% coverage). The description repeats 'up to 10 hostnames' and 'Public hostnames only' without adding format, syntax, or validation detail, so the schema carries the load.

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: TLS certificate expiry lookup for hostnames, plus the fields returned (issuer, validity dates, days left, DNS names, status). It is not differentiated from closely related siblings such as certs, domain, subdomains, headers, or uptime, so an agent must infer the boundary.

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?

Usage is implied by the scope statements ('up to 10 hostnames', 'Public hostnames only') and by the negative caveat that this is not the certificate the server presents. There is no explicit when-to-use or when-not, and no named alternative tool for the overlapping cases.

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