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

Annotations already declare readOnly, idempotent, openWorld and non-destructive, so safety is covered. The description adds genuinely useful context beyond that: k-anonymity via a 5-character SHA-1 prefix and the warning that the password travels in the request URL. It stops short of stating rate limits or exact return shape ('how many times' is only implied).

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 dense sentences, zero filler, with the breach-only constraint and the alternative front-loaded. Every clause 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 tool with full schema coverage, the description supplies what the structured fields cannot: the privacy model, the URL exposure risk, and the sibling relationship. The implied 'how many times' return signal is a minor gap with no output schema present.

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 coverage is 100% and the schema description already documents the k-anonymity mechanism and the URL/POST tradeoff, so the description largely restates it. Baseline 3 is appropriate when the schema carries the parameter burden.

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 and resource ('checks whether a password appears in known data breaches') plus the scope ('breach check only') and names the sibling it differs from. An agent can distinguish this from password and password_check without opening a schema.

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?

Explicitly routes the agent: password_check adds strength scoring and sends the password in a POST body, while this tool is breach-only. The schema repeats the conditional ('for real passwords, prefer password_check'), leaving no inference required.

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