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

No annotations are provided, so the description carries the full disclosure burden, and it discloses nothing: not how the change is computed, which parameter pair is consumed, whether it accepts arbitrary/numeric strings, or the shape of the result. 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?

Extremely short, but this is under-specification rather than conciseness — the sentence is a redundant repetition of the tool name and contributes no front-loadable information.

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?

With no annotations, no output schema, an ambiguous 4-parameter schema (0 required), and a purely tautological description, an agent has essentially no basis for correctly invoking this tool over its many siblings.

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?

Although schema coverage is nominally 100%, the schema descriptions are vacuous placeholders ('New to process', 'Old to process'). Worse, four parameters form two overlapping pairs (new/old vs current/previous) with zero indication of which are used or whether both are required, and the description does nothing to resolve that ambiguity. It falls below the baseline-3 case because the schema text adds no real meaning.

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 'Percentage Change: Percentage Change' merely restates the tool name/title with no verb, no scope, and no indication of what inputs it operates on. It does not distinguish itself from the many near-identical siblings such as x402-percent-change-of, x402-percent-change-array, 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?

No when-to-use guidance, no prerequisites, and no mention of any alternative despite dozens of closely overlapping percent/rate-change siblings. The agent is given nothing to route on.

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