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

With no annotations, the description carries the full behavioral burden and discloses almost nothing. It does not state accepted input format (the schema declares strings, not numbers), rounding/precision of the result, handling of negatives or unit suffixes, or what the response contains.

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 short, front-loaded sentence with no padding. The 'Km To Miles:' prefix largely restates the tool name, a minor redundancy but not harmful.

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?

No annotations, no output schema, and two undocumented parameters means the description should compensate and does not. A caller cannot tell which parameter to fill or what comes back, so the definition is incomplete for even this simple tool.

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 string parameters, 'km' and 'value', whose relationship is never explained. The description hints that 'km' is the input, but leaves 'value' entirely unexplained, which is a genuine ambiguity for a caller.

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 specific verb (Convert) and both units (km to miles), so the operation is unambiguous. It makes no attempt to distinguish itself from near-identical siblings such as x402-miles-to-km, x402-units-convert, or x402-metric-imperial, leaving routing to the tool name.

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 when-to-use, when-not-to-use, or alternative guidance. An agent choosing between this and the generic x402-units-convert or x402-metric-imperial gets no help from the description.

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