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

No annotations exist, so the description carries the full burden, and it only adds a pricing note ('5 free trial calls per signed wallet'). It says nothing about return format, rounding/precision, or whether rate is a decimal or percentage — the single most likely source of a wrong call. For a calculator with zero annotation coverage, this is thin.

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?

One tight, front-loaded sentence defining the computation, followed by a short trial note. No padding; the only cost is that the brevity leaves gaps elsewhere.

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 5-parameter financial calculator with no annotations, no output schema, and no parameter descriptions needs the description to disambiguate fv vs future and n vs years and to specify rate units. It does none of these, so an agent cannot call it correctly with confidence.

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?

With 0% schema coverage across 5 parameters, the description must compensate, and it only loosely maps 'future value', 'annual rate', and 'number of years' to fv/rate/years. It gives no guidance on the remaining 'n' and 'future' parameters, which appear to duplicate years and fv — a genuine ambiguity the agent cannot resolve from either structured data or prose.

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 ('Discounts a future value back to present value at an annual rate over a number of years'), which unambiguously identifies the discounting computation. It does not distinguish itself from close siblings like x402-future-value or x402-npv-calc, but the purpose itself is clear.

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?

The description implies when the tool applies (you have a future value, a rate, and a horizon) but never states exclusions or points to the inverse/related tools such as x402-future-value or x402-annuity-pv. Usage must be inferred from the formula name.

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