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

With no annotations, the description carries the full disclosure burden; it does add genuinely useful behavioral information in the form of a paywall/quota notice (5 free trial calls per signed wallet), which tells the agent that a signed wallet and paid calls are involved. It says nothing about how unsupported or malformed units are handled, whether the call is read-only or mutating, or what error/response behavior to expect.

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?

The text is two short sentences, front-loaded with the action and followed by the pricing note, with no filler. It is efficient, though the brevity is partly under-specification rather than disciplined concision.

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 tool with zero annotations, 0% schema coverage on both parameters, and no output schema, the description should specify accepted units and the value format. As written, an agent must guess what to put in `unit` and `value`, which is a material gap for a call it will otherwise invoke blindly.

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% and there are two parameters, yet the description never explains the `unit` parameter (which source units are accepted, and whether "kph" itself may be passed) or why `value` is typed as a string rather than a number. The single most important ambiguity for a conversion tool — the accepted input units — is left entirely 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?

"Convert speed to kph" states a concrete verb and target unit, so an agent knows the transformation direction immediately. It does not, however, distinguish this from the many adjacent siblings such as x402-speed-convert, x402-units-convert, x402-kph-to-knots, or x402-kph-to-mps, so the direction/specialization has to be inferred from the slug alone.

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 on when to pick this over the generic x402-units-convert or x402-speed-convert, and no statement of prerequisites beyond the trial note. The only context offered is a pricing line ("5 free trial calls per signed wallet"), which is not a use-case rule.

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