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

No annotations are supplied, so the description carries the full behavioral burden. It does add useful non-schema context — that calls are paid-metered with 5 free trial calls per signed wallet, implying an auth/wallet requirement — but it says nothing about output shape, rounding, precision, or how invalid input is handled, which matters for an unannotated tool.

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?

Two short fragments, front-loaded with the operation and free of filler prose. The emoji trial-call tagline is boilerplate but compact, so it does not meaningfully dilute the definition.

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 math tool this is close to sufficient, and no output schema means return values need not be described. However, 'tons' is ambiguous (metric tonne vs short ton vs long ton) and the accepted input format for the string 'value' is never clarified, leaving real room for a wrong call.

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?

There is one parameter, 'value', with 0% schema description coverage, and the description says nothing about it. An agent is left to infer whether it accepts '2.5', '2,5', negative numbers, or a unit-bearing string like '3 t', even though the schema types it as a string — the discrepancy is unaddressed.

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?

States a concrete verb and resource pair ('Convert tons to kg'), so the transformation direction is unambiguous and it is distinguishable from the sibling x402-kg-to-tons. It never explicitly names alternatives, but the name-plus-description pair leaves no doubt about what it does.

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 or when-not-to-use guidance is offered. The sibling list contains x402-kg-to-tons, x402-units-convert, x402-metric-imperial and x402-weight, and the description does nothing to tell an agent which of these to pick for a reverse conversion or a general unit conversion.

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