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

Annotations already cover the safety profile (readOnly, idempotent, openWorld), but the description adds real operational context: private addresses are refused and the handshake times out after 8 seconds. That timeout and the refusal rule are things an agent cannot infer from the schema or annotations, though no rate-limit or redirect/TLS-version caveats are disclosed.

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 short sentences, each load-bearing: the first gives action and outputs, the second and third give hard constraints. No preamble or restated title waste.

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 an output schema present, return-value documentation is not required, yet the description still names the reported fields. Combined with the timeout and address rules, an agent has everything needed to call it correctly and predict failures.

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 100% for the single 'host' parameter, so the schema already documents that only port 443 is contacted and private addresses are refused. The description largely restates that constraint rather than adding new semantics such as accepted URL forms or IPv6 handling, so the baseline 3 applies.

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?

Specific verb plus resource: 'Connect to a public host on port 443 and report certificate expiry, subject alternative names, protocol, and chain.' It enumerates exactly what is returned, which cleanly separates it from network-adjacent siblings like lookup_dns and check_http_headers without needing to name them.

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?

Usage is implied by the scope constraints (public host, port 443 only, private addresses refused), which tells the agent when the tool will fail. However, it never explicitly says when to choose this over lookup_dns or check_http_headers, and gives no exclusions beyond the address restriction.

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