Check Email Breaches

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

Annotations already declare the tool readOnly, idempotent, and non-destructive. The description adds useful operational context beyond those annotations: the call depends on an external service (HaveIBeenPwned) and requires a specific API key. Rate limits or failure behavior are not disclosed, but the added dependency note is valuable.

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 a single sentence with no filler, front-loads the core action, and includes the key prerequisite. Every word earns its place.

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 single-parameter, read-only lookup with an output schema and rich annotations, the description is largely sufficient: purpose, target resource, external service, and required credential are all present. The only notable gaps are API-key handling and alternative-tool guidance, but these are secondary given the tool's simplicity.

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 0%, so the description must compensate for the single 'email' parameter. It only restates that the tool checks 'an email' without adding format expectations, normalization behavior, or validation semantics, providing little value beyond the schema property name and the tool name.

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 specific verb ('Check'), a resource ('an email'), and the external data source ('HaveIBeenPwned breaches'), so the operation is clear. It does not explicitly distinguish itself from siblings like check_password_breach, but the email-vs-password difference is reasonably implied.

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 use case is implied by the description: check an email against HIBP breaches. However, the description does not mention when not to use it, does not name alternatives, and only adds the prerequisite 'needs HIBP_API_KEY' rather than guidance for choosing between similar email-related tools.

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