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

Annotations already declare readOnlyHint=true, destructiveHint=false, and idempotentHint=false, but the description adds substantial context the annotations cannot convey: cryptographic randomness source, nothing stored or logged, per-call pricing, failed calls free, and that repeats are charged. This is exactly the value-add expected beyond structured fields.

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?

Front-loaded with the core capability, then usage, example, and pricing in a compact sequence. The pricing sentence is long and slightly duplicative ('each call is charged, so repeats are not free' restates the $0.003/call line), but overall efficient for the information conveyed.

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 zero-required-param generator with no output schema, the description covers what is produced, how randomness is sourced, the cost model, and the side-effect profile. Nothing material an agent needs to invoke it correctly is missing.

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 count/length/symbols semantics are already documented in the schema; the description's example (length=20, symbols=true, count=1) illustrates but does not extend that meaning. It also mentions 'passphrase-style strings,' which no parameter actually supports, adding a minor mismatch. Baseline 3 is appropriate.

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+resource ('Generate strong random passwords or passphrase-style strings') and scopes it with 'choose length and character sets, from a cryptographic random source.' An agent can distinguish this from siblings like random_number, random_color, or uuid 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?

'Use when creating accounts or secrets' gives a clear positive trigger, and the pricing note ('each call is charged, so repeats are not free') warns against redundant invocation. It does not name a when-not case or a specific alternative sibling, so it falls short of a 5.

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