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

With no annotations, the description carries the full behavioral burden. It does disclose the actual computation (part ÷ whole) and that the result is a proportion rather than a percent, which is useful. It says nothing about edge cases such as whole = 0, precision/rounding, or the concrete output format, leaving meaningful gaps for a tool with no annotation coverage.

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 definition is a single front-loaded sentence with the operation stated first. The appended free-trial emoji/promo adds noise that does not help tool selection, keeping it out of the top score.

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 two-parameter math utility with no annotations and no output schema, the description covers the operation but omits output format (decimal ratio vs. percent vs. rounded value) and division-by-zero behavior. Given the dense field of near-identical ratio/percent siblings, these omissions matter for correct invocation.

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%, so the description must compensate. 'Part divided by the whole' does clarify the role of each parameter (part = numerator, whole = denominator), which is real added meaning beyond bare names. It does not specify accepted input formats (numeric strings, fractions, decimals) or whether the values can be non-numeric.

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 concrete operation (part divided by the whole) and names the resource (a proportion), so an agent can tell what it computes. However, it does not distinguish itself from close siblings such as x402-ratio-of, x402-percent-of, and x402-percentage-of, which an agent would need to choose between.

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 statement of when to use this tool versus the many related ratio/percent siblings, and no preconditions or exclusions. The only additional sentence is a pricing promo ('5 free trial calls per signed wallet'), 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.