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

With no annotations the description carries the full burden; it does disclose the underlying computation and the payment model (5 free trial calls per signed wallet), which is real behavioral context. It omits expected units, output format, and behavior on missing/zero time, so coverage is partial.

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 definition is front-loaded with the core computation in one short sentence, followed by the input hint and pricing note. Little is wasted, though the emoji pricing line is boilerplate unrelated to the calculation itself.

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 two-parameter arithmetic tool this covers the essentials of what to supply and how it is computed. The significant gap is units and output format, which matter for a physical quantity like velocity, especially with untyped string parameters.

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%, so the description must compensate. The formula pins down that distance is the numerator and time the denominator, which is more than the bare schema gives, but it says nothing about acceptable units or the string format both parameters require.

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 and resource plus the exact formula (distance divided by time), so the operation is unambiguous. However, it does not distinguish itself from close siblings such as x402-speed, x402-wave-speed, or x402-angular-velocity, leaving the agent to guess which velocity-like tool to pick.

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?

"Provide distance and time values" is input instruction, not usage guidance. There is no statement of when to prefer this over x402-speed or x402-angular-velocity, and no prerequisites or exclusions beyond the payment note.

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