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

Goes well beyond the annotations by disclosing the data source (public Certificate Transparency logs via Cert Spotter with crt.sh fallback, not the live connection), the resulting caveat that a brand-new cert may not appear yet, the resource footprint (one HTTPS request plus one CT query, 1-5 s), and the billing model ($0.01 USDC via x402, payment in _meta['x402/payment'], errors not charged). This is exactly the operational context annotations cannot express.

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?

Four sentences, each carrying distinct load: purpose/outputs, sibling routing, data-source caveat, and cost/latency/error behavior. Scope and primary behavior are front-loaded ahead of the caveats, with no 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?

With no output schema, the description carries the return-value burden and does so by naming the fields returned. For a read-only, single-parameter probe it also covers timing, cost, failure semantics, and the data-source limitation that affects interpretation of 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 100% for the single 'domain' parameter, so the schema already documents accepted formats (hostname or URL). The description's 'one hostname' phrasing reinforces single-target scope but adds no syntax or format detail beyond what the schema provides, so baseline 3 applies.

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 ('Check the TLS certificate of one hostname') and enumerates the exact output fields (issuer, validity dates, days left, % of lifetime used, renewal-stall flag, HTTPS probe). It explicitly distinguishes itself from sibling tools site_health and domain_grade, so an agent can route without opening a schema.

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?

Gives an explicit when-to-use ('when you only need certificate health') paired with the alternatives and the condition that selects each: site_health for cert + DNS + expiry together, domain_grade for a scored A-F result. Nothing is left to inference.

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