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

Annotations already declare readOnlyHint=true and openWorldHint=true, so the agent knows this is a safe outbound network read. The description adds useful behavioral value by listing what is returned (validity, issuer, expiry, days remaining, SAN) in the absence of an output schema. It does not disclose what happens when the certificate is invalid, self-signed, or the host is unreachable, which matters for a network probe.

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 compact fragment with zero filler, front-loaded with the resource and followed by the returned fields. It is terse to the point of being telegraphic, but nothing in it is wasted.

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 two-parameter network probe with no output schema, the description does cover the return contents, which is the main gap-filler. However, it omits port defaulting, failure semantics (bad/expired cert, connection refused), and any expectation of latency, so an agent cannot fully predict behavior.

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 coverage is only 50%: host is documented in the schema ('Hostname or public IP'), but port has no description anywhere. The description adds no parameter detail at all, so the common question of what port defaults to (443) and whether a non-standard port is supported is left unanswered. With low coverage the description should have compensated and 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 a specific resource (the TLS certificate of a host) and enumerates the exact facts it surfaces: validity, issuer, expiry, days remaining, SAN. That is enough to distinguish it from siblings like dns_lookup or whois. It is a noun phrase rather than a verb, but the resource and output are concrete.

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 guidance on when to reach for this tool versus dns_lookup, whois, or http_headers, and no mention of prerequisites or exclusions. The only implicit cue is that it is certificate-focused, leaving the agent to infer the use case.

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