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

No annotations are provided, so the description must carry the behavioral disclosure burden. It does not disclose what the output looks like, whether the operation is synchronous, rate limits, or any limitations of the XposedOrNot source. The only behavioral hint is 'no key', which is more a requirement than a behavior. This is a significant gap for a lookup tool with no annotation support.

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 that is efficient and front-loaded with the core purpose and the key differentiator. It could be slightly more descriptive, but it is appropriately sized and wastes no words.

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?

An output schema exists, so return values are presumably covered. However, the input is not explained; the description does not clarify that 'q' expects an email address. For a simple lookup tool, this is a critical omission. The description leaves an agent guessing about the parameter format and usage.

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 schema has a single parameter 'q' with 0% coverage, and the description does not explain what 'q' represents. The tool name and description imply it takes an email address, but the parameter is never explicitly described. With no schema descriptions, the description must compensate, and it fails to do so.

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 clearly states the tool checks email breach exposure via XposedOrNot, mentioning it is HIBP-compatible and requires no key. This distinguishes it from tools like hibp_breaches that may require an API key. However, it does not explicitly differentiate from several similar breach-checking siblings such as breach_aggregator or breachsearch, so it loses a point.

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 description implies a use case: querying email breach data without an API key. It mentions 'no key' which is a differentiator, but it does not explicitly state when to use this tool versus alternatives like hibp or breach_aggregator, nor any conditions for selecting this tool. The guidance is more implied than explicit.

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