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

Annotations already declare readOnlyHint, idempotentHint and openWorldHint, so the safety profile is covered. The description adds genuine context by disclosing that results come from a live TLS handshake (network-dependent, potentially slow/failing) rather than a local cache, but it says nothing about failure modes (no cert, TLS error, timeout) or handshake behavior.

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 essential fact (live TLS handshake on port 443) and then enumerates returned fields. No filler, though the field enumeration is largely recoverable from 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 read-only lookup with an output schema and full annotation coverage, the description supplies the key non-structured fact (live handshake vs. cached data) and the scope of returned data. Only the input domain format and error behavior are left unaddressed.

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 `domain` parameter, so the description must compensate. It only indirectly hints at parameter semantics by fixing the port at 443; it never states whether `domain` should be a bare hostname, a URL, or include a port. The output-field list does not help with input format.

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?

Names the specific resource (the TLS certificate a domain serves on port 443) and the mechanism (a live handshake), which clearly separates it from whois_lookup, dns_records and the other siblings. It is a noun phrase rather than a verb+object, so it reads slightly as a data definition, but the intent is unmistakable.

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?

"From a live TLS handshake" implicitly tells the agent this is a real-time probe rather than cached registry data, which is a useful usage cue. However, it never states when to prefer this over domain_lookup or dns_records, nor any exclusion or prerequisite, so guidance remains implicit.

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