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

Annotations already declare readOnlyHint, openWorldHint, and idempotentHint, so the safety profile is covered. The description adds real context beyond them: the data comes from an actual live TLS handshake on port 443, which tells the agent this is a network-dependent, potentially slow or failing operation. However, it says nothing about failure modes (no TLS, timeout, unreachable host) or rate limits.

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?

A single dense sentence that front-loads the core resource and mechanism before the field list. No filler, though the trailing field enumeration duplicates what the output schema likely already provides.

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 read tool with annotations covering safety and an output schema covering return structure, the definition is nearly sufficient. The remaining gap is behavioral: it omits what happens when the handshake fails or the domain has no certificate, which matters for a live-network query.

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% – the single 'domain' parameter has no description and no format hints. The description only implicitly refers to 'a domain' and does not clarify acceptable forms (bare hostname vs URL, wildcards, IP addresses, ports). With low coverage, the description should compensate but does not.

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?

The description names the concrete resource (the TLS certificate a domain serves on port 443) and the mechanism (a live TLS handshake), then enumerates the exact fields returned. An agent can tell this apart from dns_records, whois_lookup, and subdomains by the 'certificate' + 'TLS handshake' wording, though it never explicitly contrasts itself with those siblings.

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 when-to-use guidance, no exclusions, and no mention of the sibling tools. It does not say to call this when you need certificate expiry/inspection data, nor does it note any precondition (e.g. the domain must serve TLS on 443).

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