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

No annotations exist, so the description carries the full burden. It discloses a payment/auth requirement implicitly via "signed wallet", which is genuinely useful, but it says nothing about the string encoding expected for the array, how a single-element array behaves, or the output shape. Gaps outweigh the one useful hint.

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?

A single front-loaded sentence followed by a short pricing note; nothing is wasted. The leading label "Percent Change Array:" mildly duplicates the tool name, but the structure is efficient.

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 one-parameter tool with no annotations and no output schema, the description should at minimum define the input string format and the result. It covers purpose and pricing but leaves input encoding and return behavior unspecified, which is a meaningful gap at this complexity level.

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% for the single parameter "values", which is typed as a plain string with no description. The phrase "in an array" hints the content is a sequence, but the description never explains the string serialization (comma-separated? JSON?), so an agent cannot reliably construct the input.

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?

"Computes percentage change between consecutive values in an array" names a specific verb and resource, and the "array" qualifier plus the tool name distinguishes it from scalar siblings like x402-percentage-change or x402-percent-change-of. It does not explicitly route against those near-neighbors, but the purpose is unambiguous.

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 guidance is the pricing line ("5 free trial calls per signed wallet"); there is no statement of when to choose this over x402-percentage-change, x402-percent-change-of, x402-diff-array, or x402-rate-of-change, and no prerequisites or exclusions.

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