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

Annotations already declare readOnly, idempotent, openWorld and non-destructive behavior, so the bar is lower. The description still adds valuable non-structured context: it makes an outbound connection to port 443 and requires no account, which tells the agent about network dependence and auth needs. It does not mention failure modes for unreachable or expired certificates.

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?

Two sentences, no filler, and the behavioral facts (port 443, returned fields) are front-loaded before the auth note. Every clause contributes information an agent would otherwise have to guess.

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?

There is no output schema, so the description compensates by enumerating the returned fields — issuer, validity dates, days until expiry, covered names. Combined with the auth disclosure and the fully documented single parameter, an agent has everything needed to call this correctly.

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% for the single 'domain' parameter, including the note that a URL or www prefix is accepted and stripped. The description adds no parsing or format detail beyond that, so the schema does all the work and the baseline of 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?

States a specific verb and resource — connects on port 443 and returns issuer, validity dates, days until expiry and covered names. The scope is unambiguous, though it never names a sibling it is distinguished from; the 'no TLDix account' note only implicitly separates it from account-scoped tools.

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?

The line 'Does not need a TLDix account' tells the agent this tool requires no authentication, which is genuine usage context. However, there is no statement of when to prefer this over lookup_domain or check_domain_expiries, and no exclusion conditions, so guidance is only implied.

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