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

Annotations declare readOnlyHint=true, idempotentHint=true, and destructiveHint=false, so the agent knows it's a safe read operation. The description adds important behavioral context: it warns that a prefix alone cannot identify an account and that local comparison is required, which is beyond what annotations provide. This transparency helps the agent understand the purpose and limitations of the operation.

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 sentences, no fluff. The first sentence states the action and the second provides the critical prerequisites and caveats. It is front-loaded with the essential action, then covers the necessary operational detail. 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?

Given the tool uses a non-trivial k-anonymity protocol and has a rich schema (with enums, defaults, and a custom response format), the description covers the essential usage context: authentication requirement, the local comparison step, and the endpoint nature. The output schema is present, so return values don't need explanation. The description is complete for an agent to call the tool correctly.

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 100%, so the schema already documents all parameters. The description adds value by explaining the security rationale for the prefix parameter and the local comparison requirement, which is not in the schema. The 'response_format' parameter is also explained in the schema (markdown vs JSON, structuredContent always returned). The description reinforces the key semantic of the prefix parameter beyond the basic pattern.

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 ('Query'), a specific resource ('HIBP k-anonymity breached-account range endpoint'), and a precise mechanism (first 6 characters of SHA-1 email hash). It clearly distinguishes from the sibling tool 'hibp_get_breached_account' by naming the k-anonymity range endpoint and the hash-prefix approach, which is a different API call.

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 explicitly states a prerequisite ('Requires a subscription with k-anonymity access') and gives a critical usage instruction (compare returned suffix with remaining hash characters locally). It doesn't explicitly contrast with the sibling tools, but the purpose clarity already differentiates it from the direct account lookup. The when-to-use context is clear enough.

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