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

Goes well beyond the annotations by defining the 'warn' (expiring within 30 days) and 'bad' (expired or down) status semantics, disclosing a 15-minute cache, and stating the rate limit of 15 fresh lookups per 10 minutes. Annotations already cover read-only/idempotent/non-destructive, and the description adds the operational constraints an agent needs to avoid throttling.

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 front-loaded sentences: first the returned data, then the triggering questions, then status codes and caching/rate limits. No redundant restatement of the title, and every sentence contributes operational value.

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?

Output schema exists, so return formatting needn't be explained, and the description still covers status thresholds, caching, and rate limits for a one-parameter read tool. Nothing an agent needs to call it correctly is missing.

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?

The single 'domain' parameter is fully described in the schema (hostname or URL with examples) at 100% coverage, so the description neither needs to nor does add format or syntax detail. Baseline 3 applies since the schema carries the parameter burden.

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?

Uses a specific verb ('Look up') with an enumerated resource set: SSL certificate expiry (date, days left, issuer), domain registration expiry (date, days left, registrar), and HTTP status. The exact returned facts are named, so an agent can distinguish this from get_plans and start_monitoring without opening a schema.

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?

Explicitly states when to use it: when someone asks when a site's certificate or domain expires, who issued it, or whether the site is up. No when-not-to-use or named alternative is given, but the sibling tools are unrelated enough that the trigger conditions suffice.

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