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

No annotations exist, so the description carries the full burden. It usefully discloses the output shape (hex digest) and the keylen default of 32, plus a trial/payment notice, but omits determinism, error behavior for missing inputs, and cost beyond the free trial.

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 operation and inputs in one sentence, followed by output/default info; no filler beyond the short trial-call tagline, which carries commercial rather than operational value.

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 simple three-parameter hash tool with no output schema, the description covers inputs, output format, and the one optional parameter's default, which is enough to call it correctly. Only the keylen string-vs-number ambiguity and lack of alternative guidance keep it from a 5.

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 0%, yet the description names all three parameters, marks keylen optional, and supplies the default value 32, adding genuine meaning the schema lacks. It does not clarify why keylen is typed as a string in the schema despite the numeric default, which is the one remaining gap.

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 algorithm ('Derive a scrypt password hash from a password and salt') and names the return value ('hex digest'), which lets an agent distinguish it from the sibling pbkdf2/hash tools by algorithm. It stops short of explicitly contrasting with those siblings, so a 4 rather than a 5.

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?

It says to supply password and salt, but gives no when-to-use guidance relative to alternatives such as x402-pbkdf2 or x402-hash, nor any prerequisite or exclusions. Usage is only implied by the algorithm name.

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