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

No annotations are provided, so the description carries full burden. It does not disclose input format expectations (array vs comma-separated string), sign conventions for cashflows, whether initial investment should be negative, units for rate (decimal vs percent), or output format. 'Provide cashflows and rate' is an instruction but not behavioral context.

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 description is two sentences, one stating purpose and one instructing the user. It is front-loaded and efficient; no wasted words. It loses one point because it misses the opportunity to disambiguate the redundant parameter names.

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 financial calculation tool with no output schema and four optional string params, the description is too thin. It doesn't explain the expected format of the cashflow series, the rate format, sign conventions, or how the tool responds. An agent is likely to guess wrong on which param to use, given the duplicate pairs.

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 describes 4 string params with vacuous descriptions ('Rate to process'), and schema coverage is 100%. The description introduces the semantic pair 'cashflows and discount rate' but doesn't cleanly map to the four params: 'rate' vs 'discountRate' and 'flows' vs 'cashflows' are redundant. A caller cannot tell which param to populate. The description says 'cashflow series and discount rate' but does not say whether to use 'rate' or 'discountRate'.

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?

The description states a specific verb/resource: 'Calculate Net Present Value (NPV) from a cashflow series and discount rate.' It clearly distinguishes this tool from the large x402 sibling set, though it doesn't explicitly contrast with related financial tools like x402-present-value or x402-irr-calc.

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?

No when-to-use guidance is provided. The name contains 'npv-calc' and the description explains what it does, but there is no explicit direction about when to prefer this over alternatives like x402-present-value, x402-future-value, or x402-irr-calc. Schema properties are all optional, so an agent gets no required-input guidance.

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