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

Annotations already declare readOnlyHint/idempotentHint/destructiveHint=false, so the safety profile is covered. The description adds genuinely useful behavior beyond that: breach lookup uses k-anonymity with only a hash prefix transmitted, the password travels in a POST body rather than a URL, and any breached password is deterministically rated very_weak regardless of other factors. It stops short of describing the scoring scale or return shape, which keeps it from a 5.

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 core function is front-loaded in the first clause, and the routing/privacy sentences follow. The single paragraph is dense with no filler; it runs slightly long, but every clause carries information an agent would otherwise have to infer.

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 2-param read-only tool with no output schema, this covers purpose, alternatives, privacy/transport, and the deterministic breach rule — enough to invoke and interpret it correctly. The only gap is that it never characterizes the returned score (numeric range, label set) or the breach count, which the agent will have to discover from the response.

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 the baseline is 3, but the description adds real meaning beyond the schema: check_breach isn't just 'check against breach corpora' — it specifies the k-anonymity mechanism and the hard rule that a breach hit forces a very_weak rating. That materially changes how an agent should interpret the result.

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 ('Scores a password's strength') and enumerates the factors used (length, character variety, entropy as an upper bound, repeated patterns, per-word passphrase estimation). It also differentiates itself from the adjacent siblings password_breach and password, so an agent can select it without opening any 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?

Explicit routing: 'Use it to evaluate a password someone is choosing; use password_breach when you only need the breach count, and password to generate a new one.' This names both alternatives plus the condition that selects each, which is exactly the when-to-use guidance an agent needs.

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