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

Beyond the readOnlyHint annotation, the description adds rich behavioral details: the password is SHA-1 hashed locally, only the first 5 hash characters are sent to HIBP, the password never leaves the server, is never stored or logged, and the return value indicates found status and frequency. This significantly enhances transparency.

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 three sentences, each earning its place: the first states the core purpose, the second explains the privacy mechanism, and the third states the return type. No redundant or filler content.

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 tool with readOnly/openWorld hints, the description is complete: it explains the operation, the security behavior, and the return value. The absence of an output schema is mitigated by the explicit mention of what the tool returns ('whether it was found and how many times').

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 description already covers the 'password' parameter at 100% coverage, but the tool description adds critical semantic details: the hashing algorithm (SHA-1), the truncation to 5 characters, and the explicit guarantee that the password is never transmitted or stored. This goes beyond the schema's summary and provides practical understanding.

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's purpose: 'Check whether a password has appeared in known breaches using HIBP k-anonymity.' It uses a specific verb (check) and resource (password), and the mention of HIBP and k-anonymity distinguishes it from sibling tools like dp_check_domain_breaches and dp_check_email_security.

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 provides clear context for when to use the tool—when you need to verify if a password is breached—and explains the privacy-preserving method. However, it does not explicitly mention alternatives or exclusions, though sibling tools cover different domains (email, domain, whois), so the usage scenario is implied.

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