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

Annotations already declare readOnly, idempotent, openWorld and non-destructive, so the safety profile is covered. The description adds genuinely useful behavior beyond that: only breach names are returned and passwords are never returned, which sets expectations about result sensitivity and scope.

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 short sentences, front-loaded with the core action, followed by the return-content and privacy clause. Every sentence earns its place with no filler.

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 low-complexity, single-parameter read-only lookup, the description covers purpose, safety context, and return content, while annotations handle the side-effect profile. Absent an output schema, the explicit statement that only breach names are returned fills the remaining gap.

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?

There is a single required 'email' parameter with 100% schema description coverage, so the schema fully documents the input. The description adds no format, normalization, or validation detail beyond what the schema already provides, making the baseline 3 correct.

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 (check) plus the exact resource and scope: an email address against the XposedOrNot index of known public data breaches. The email-level framing implicitly separates it from domain-level siblings like domain_breach_summary and from list_breaches.

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 name and the 'email address' scope, which is enough to infer this is the per-email lookup rather than a bulk or domain tool. However, there is no explicit when-to-use, when-not-to-use, or named alternative (e.g. versus domain_breach_summary), so the agent must infer routing on its own.

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