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

With no annotations, the description carries the full burden and does disclose two important behavioral traits: the data comes from a live HTTPS check plus Certificate Transparency logs, and the call is paid (0.01 USDC on Base via x402, or 12 sats via Cashu NUT-24 or Lightning L402). It omits failure modes for unreachable/non-TLS hosts, latency, and whether results are cached, which keeps it short of a 5.

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 sentences, zero waste: the first front-loads what is returned and the data sources, the second packs the payment options. Nothing is repeated from the schema or padded.

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 annotations, no output schema, and one undocumented parameter, the description covers the two biggest agent questions — what comes back (field list) and what it costs (all three payment rails). It falls short only on error behavior for invalid or non-HTTPS hosts.

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 0% for the single required parameter, so the description must compensate. It says the value is a host, which conveys the semantic meaning of the field, but gives no format guidance (bare hostname vs URL vs host:port), so an agent could still pass a malformed value.

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 resource (TLS certificate details for a host) and enumerates the exact fields returned — subject, issuer, SANs, validity dates, days to expiry. It is unambiguous about what the tool does, but never names or contrasts a sibling such as dns_lookup or headers, so sibling differentiation is left to inference.

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?

There is no statement of when to use this tool versus the many other host/domain-oriented siblings, nor prerequisites about when a live HTTPS check applies. The payment-method sentence hints at cost but gives no guidance on which rail to choose or when the tool is the right call.

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