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

Annotations already cover readOnly and openWorld safety. The description adds genuinely useful non-schema behavior: answers cached for an hour, one request per call, a per-success price of $0.002 USDC via x402 with named payment chains, and that failed calls are not charged. Only the return-shape detail overlaps what the output schema likely carries.

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-loaded with the returned fields, then operational and pricing details in a compact flow. Slightly dense but every clause (caching, 100-DNS-name cap, billing) carries information; nothing is pure filler.

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?

Output schema exists so return values need not be described, yet the description still enumerates returned fields and caps. With annotations covering safety and the description covering cost/caching/rate behavior, an agent has enough to call it correctly; only explicit sibling routing is missing.

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?

Single `domain` parameter with 100% schema description coverage ('Domain name, e.g. example.com'). The description adds no format constraints, TLD handling, or normalization rules, so it neither helps nor hurts beyond the schema baseline.

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+resource (TLS certificates for a domain) and names the data source (Certificate Transparency logs via CertSpotter), which implicitly distinguishes it from the live-check sibling `ssl`. It does not explicitly say how it differs from `subdomains` or `ssl`, so a little inference is required.

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?

No when-to-use or when-not guidance. The description never tells the agent to prefer this over `ssl` (live TLS check) or `subdomains`, despite clear overlap with both siblings. Only operational constraints (one request per call, cached an hour) are given.

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