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

With no annotations, the description carries the full burden. It discloses the live-handshake behavior, the fixed port, the return surface, and — importantly — the commercial/rate-limit envelope: 5 free calls per day across all tools and a prepaid `key` option at 0.005 USDC per call. It does not cover failure modes (unreachable host, timeout, untrusted-cert response shape), which keeps it out of 5 territory.

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?

Three sentences, no filler. The core behavior is front-loaded, the use case follows, and the pricing/rate-limit constraint is placed last where it belongs. Every clause — including the output list — earns its space given there is no 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?

No output schema exists, so the description compensates by enumerating the returned fields, and it covers cost and access. What remains thin is error/failure behavior for a live network call (unreachable host, handshake failure, untrusted chains) — minor but a real gap for an agent that must interpret an empty or failed result.

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 100%, so the baseline is 3. The description earns above baseline by adding meaning the schema does not: `key` unlocks a prepaid balance at 0.005 USDC per call, and the target is implicitly fixed to port 443, which constrains how `domain` is used.

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 concrete action and resource: 'Live TLS handshake with a host on port 443', and then enumerates the exact facts returned (trust, issuer, covered names, protocol version, expiry, days left). The purpose is unmistakable. It stops short of an explicit sibling contrast, though the scope is clearly distinct from check_domain, email_auth, etc.

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?

'Use it to catch an expiring or misissued certificate' gives a clear use context. There is no when-not guidance and no named alternative, but none of the siblings (balance, create_key, check_domain, domain_registration, email_auth, read_url, claim_deposit) plausibly compete for the same task.

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