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

No annotations are provided, so the description carries the full behavioral burden, yet it discloses nothing: not whether inputs are numbers or strings, not the formula used, not the sign convention for decreases, and not the return shape. It is a pure name echo.

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?

It is short, but that brevity reflects under-specification rather than conciseness. The redundant name repetition 'X: X' is pure filler with no informative 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 two-parameter computation tool with no annotations and no output schema must explain its semantics in prose, and this description explains nothing at all. An agent cannot determine what the tool computes or how to call 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 100% (both 'new' and 'old' have descriptions), so the baseline of 3 applies. The description itself contributes nothing to parameter meaning, and the schema's own text ('New to process', 'Old to process') is generic boilerplate, but per the rule high coverage sets the baseline at 3.

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 'Percent Change Of: Percent Change Of' merely restates the tool name, a tautology that adds no verb+resource specificity. It does not distinguish this tool from close siblings such as x402-percentage-change, x402-percent-change-array, x402-percent-of, or x402-rate-of-change.

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 guidance whatsoever on when to use this tool, when not to, or which sibling alternative to prefer. With dozens of percent/ratio tools in the sibling list, an agent gets zero routing help.

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