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

No annotations are provided, so the description carries the full burden. It states the metric but omits input encoding, behavior on empty/single-element arrays, and the return format. The '5 free trial calls per signed wallet' line is useful billing context but not a behavioral trait of the computation itself.

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?

One tight sentence leads with the operation and its formula, with no wasted prose. The pricing emoji/trial note is appended and mild but not disruptive.

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, and an undocumented string parameter, the description should clarify input syntax and return shape. It defines the metric but leaves an agent unable to construct a correct call for a string-encoded array.

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 coverage is 0% for the single 'values' parameter, and the description says 'array' while the schema declares type string, without explaining the accepted string encoding (comma-separated, JSON, etc.). This mismatch is exactly the kind of ambiguity the description should resolve, and it does not.

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 names the operation and defines the computation precisely: 'Returns the range of an array as its maximum minus its minimum.' This disambiguates it from the many nearby stat tools by spelling out the formula. It does not, however, differentiate itself from the sibling x402-range or x402-midrange, leaving the agent to guess which one applies.

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 versus alternatives, despite a near-identical sibling (x402-range) and related tools (x402-midrange, x402-find-max/min). The only guidance is a pricing note about free trial calls, which does not help tool selection.

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