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

No annotations are supplied, so the description carries the full burden. Beyond the fact that the result is a percentage, it says nothing about handling of negative ROI, rounding/precision, what happens when zero or no arguments are passed, or whether the 5-call trial limit gates the call.

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 functional content is two tight sentences with the definition front-loaded. The trailing '🆓 5 free trial calls per signed wallet' promo is relevant context but is marketing framing rather than invocation guidance.

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 two-value calculator with no output schema and no annotations, the description covers the essentials: what is computed, the output unit, and which of the four aliased params to use. The main unresolved gap is the zero-required-parameter schema and alias conflict behavior, which an agent needs to call it reliably.

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% across four string params, so the description is the only documentation — and it does clarify the cost/investment and gain/return aliasing, which is real added value. It still leaves open whether both aliases may be sent, which wins on conflict, the accepted numeric format, and why nothing is required.

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: 'Calculate Return on Investment as a percentage,' which is unambiguous about the computation and its output form. It does not, however, distinguish itself from the near-identical sibling x402-roi-calc, which an agent could equally well 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?

The sentence 'Provide cost (or investment) and gain (or return)' gives input-oriented guidance, which implicitly tells the agent what is needed to call it. There is no when-to-use/when-not-to-use framing and no routing away from the duplicate sibling x402-roi-calc.

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