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

No annotations are supplied, so the description carries the full disclosure burden. It does add one genuine behavioral trait not present in structured data: a quota of 5 free calls per signed wallet, implying a paywall and wallet-signature requirement. However, it says nothing about what the tool computes, whether inputs are combined, or what is returned.

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?

Very short and front-loaded, but roughly half the text is promotional (emoji, free-trial pitch) rather than informative. It earns brevity points but wastes the limited space on non-functional 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?

A computational tool with three undocumented parameters, no annotations, and no output schema needs the description to define the calculation and input semantics. Neither is provided, leaving the agent unable to invoke it correctly.

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 three string parameters (total, value, percent), and the description adds no meaning to any of them. An agent cannot infer whether percent is required, whether all three are used together, or what numeric format is accepted.

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?

"Percent: Percentage calculators" names the resource area but no specific operation. Against siblings like x402-percent-of, x402-percent-of-value, x402-percentage-of, and x402-percentage-change, an agent cannot tell which percentage computation this tool performs.

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 only added sentence concerns free trial calls per signed wallet, which is a payment note rather than when-to-use guidance. There is no indication of when to pick this over the many percent-related siblings, and no prerequisites beyond the implied wallet signing.

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