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

Annotations already declare readOnlyHint, openWorldHint and destructiveHint=false, so safety is covered. The description adds genuinely new behavior: a cost of 5 credits and that the result set is tier-dependent (paid plans expose seen-count and risk level), which affects how an agent should interpret the response.

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?

Four short sentences, front-loaded with the purpose before the input choices and the paid-tier/cost caveat. Minor waste in the 'Password Breach Checker: Password Breach Checker' repetition of the title.

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?

The tool is simple (two optional string params, output schema present), and the description covers the source corpus, the tier-dependent outputs, and the credit cost. Since an output schema exists, the description need not enumerate return fields in detail, so the remaining gap is small.

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%, so both parameters are already documented with examples and the 'send this or hash' note. The description merely restates the either/or choice without adding format guidance such as case sensitivity for the hex hash, so the baseline of 3 applies.

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 ('tells you whether a password appears in the Pwned Passwords corpus') and names the exact data source. It is unambiguous and distinguishable from neighbors like PasswordStrength and PasswordGenerator, which measure or create rather than check against a breach corpus.

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?

Usage is only implied: it accepts either a plaintext password or its hash, and mentions that paid plans return extra fields. There is no explicit guidance on when to prefer this over PasswordStrength, nor any when-not condition, so an agent must infer the selection rule.

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