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

No annotations are present, so the description carries the full burden of behavioral disclosure. It reveals nothing beyond the conversion intent — no mention of precision, rounding, output format, or side-effect-freedom, and it fails to clarify how the miles value is supplied given the tool exposes an empty input schema. This is a significant gap for a tool with zero annotation coverage.

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 description is extremely compact and front-loaded, but roughly half of it ('Miles To Km:') redundantly restates the tool name, so not every token earns its place. The message could be fully delivered by 'Convert miles to km' alone.

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 converter with an empty input schema and no output schema, the description leaves critical mechanics unaddressed: how the agent provides the miles value and what the return value looks like. An agent can disambiguate direction from the name, but cannot determine how to correctly invoke the 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?

With zero parameters in the schema, the rubric sets a baseline of 4; there are no parameter semantics to misstate. The description adds no parameter-level detail, but the empty schema leaves nothing to document — a 5 would have required explaining how the miles input is actually passed to the tool.

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 core clause 'Convert miles to km' states a specific verb and resource, and the one-way direction makes it inherently distinguishable from the reverse sibling x402-km-to-miles. However, the leading 'Miles To Km:' prefix merely restates the tool name, and there is no explicit differentiation from general conversion tools like x402-units-convert.

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 description provides no guidance on when to use this tool versus the many conversion siblings (x402-km-to-miles, x402-units-convert, x402-metric-imperial, x402-speed-convert). No conditions, exclusions, or alternative routing is offered, leaving the agent to guess based on the name alone.

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