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

With no annotations, the description carries the full behavioral burden, yet it only adds the quota note ("5 free trial calls per signed wallet"), which is genuinely useful context. It says nothing about output shape, assumed period spacing of the cashflow series, discount-rate convention (decimal vs percent), validation failures, or what happens after the trial is exhausted.

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 sentence is front-loaded and wastes no words, which is good. The trial-call tagline and emoji add promotional noise to a three-sentence description without resolving any of the real gaps.

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?

A four-parameter, all-string, no-required schema with duplicate-looking fields and no output schema demands more explanation than this. The description omits which parameter names are correct, the rate format, and what the result looks like.

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 description coverage is 0% and nothing is required, so the description must compensate. It names only "cashflows" and "rate" while the schema exposes four fields including apparent duplicates (flows/cashflows, rate/discountRate), leaving the agent unable to tell whether these are aliases or distinct inputs — the most consequential ambiguity in this tool.

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 gives a specific verb and resource ("Calculate Net Present Value (NPV) from a cashflow series and discount rate"), which is unambiguous on its own. It does not differentiate from close siblings such as x402-present-value, x402-irr-calc, or x402-future-value, so an agent must infer which valuation tool to pick.

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?

"Provide cashflows and rate" is parameter instruction, not usage guidance. There is no statement of when to use this versus x402-present-value or x402-irr-calc, no preconditions, and no exclusions.

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