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

Annotations already cover read-only, idempotent, non-destructive and closed-world behavior, and the description usefully corroborates the closed-world claim by stating there is no external lookup. It also discloses the qualitative nature of the result ('heuristic assessment, not a breached-password check'), which annotations alone cannot convey. It stops short of describing the actual output shape.

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?

The description is short and front-loads the action ('Evaluate strength'), but two of its four clauses say essentially the same thing about not sending real credentials to an external/third-party endpoint, which is redundant padding rather than an additional constraint.

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 one-parameter validator with full schema coverage and rich annotations, the safety and scope context is adequate. However, there is no output schema, so the description carries the burden of explaining the return value and only says it is a 'heuristic assessment' without indicating whether the result is a boolean, a score, or a strength tier.

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?

With a single parameter at 100% schema description coverage, the schema already documents the 'password' field including the dummy-value warning. The description restates the same warning rather than adding format, length, or validation semantics beyond what the schema provides, so 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?

The description states a clear verb+resource ('Evaluate strength') and qualifies it as a heuristic assessment rather than a breached-password lookup, which sets it apart from a network-backed checker. It does not explicitly contrast with the is-*safe sibling family (is-email-safe, is-uuid-safe, etc.), so sibling differentiation is implicit through the naming pattern rather than stated.

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?

It gives concrete usage conditions: use only with dummy passwords, to evaluate upstream password rules, and never with real user credentials. That is a strong when-to-use/when-not-to-use constraint, though no alternative tool is named for cases where a real breach check is actually wanted.

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