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

No annotations are provided, so the description carries full behavioral burden. It discloses the computation and hints at a payment gate ('5 free trial calls per signed wallet'), but says nothing about rounding, precision, division-by-zero handling, or what is returned. For a tool with a wallet-signing requirement, that payment/auth context 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?

The core formula is front-loaded in a single efficient clause and the whole description is short. The appended emoji/promo sentence is minor noise but does not bury the useful content.

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?

This is a trivial two-parameter arithmetic tool with no output schema and no nested objects, so the description is nearly sufficient. It still omits the return format (raw number vs. '50%') and edge-case behavior, which matters more here because no output schema pins those down.

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 both parameters (total, value) are bare strings. The description partially compensates by naming both parameters and their roles in the formula, which is more than the schema offers, but it never states that inputs are strings, whether decimals are allowed, or how many decimal places the result carries.

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 operation (value divided by total, times 100) rather than restating the name, so an agent knows exactly what math is performed. However, the sibling list contains near-identical tools (x402-percent-of-value, x402-percentage-of, x402-proportion-of, x402-ratio-of), and the description does nothing to distinguish this one from them.

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?

There is no when-to-use guidance, no prerequisites, and no mention of an alternative such as x402-percent-of-value or x402-percentage-of. The only additional sentence is a promo line about free trial calls, which is not usage guidance.

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