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

No annotations are provided, so the description carries the full behavioral burden. It discloses the computation and the 5-free-call wallet policy, but says nothing about accepted units, expected magnitude/format of the string inputs, output shape, or error behavior for a physics calculation where unit assumptions are critical.

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 compact sentence leads with the purpose and formula, followed by a short pricing note. Nothing is bloated, though the trial-call emoji line is promotional rather than functional.

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 numeric tool with no annotations and no output schema, the description should at minimum pin down units and result format. It leaves both unspecified, so an agent cannot confidently invoke it without guessing.

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%, so the schema gives no help. The description partially compensates by mapping both parameters conceptually: speedLight is the speed of light and mediumSpeed is the speed in the medium. However, it never states units (m/s vs km/s) or string format, which is the key ambiguity for these parameters.

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 description names a specific quantity and even states the exact formula (speed of light divided by speed in the medium), so an agent knows precisely what is computed. It does not, however, distinguish this tool from look-alike siblings such as x402-light-speed, x402-speed, or x402-wave-speed, leaving the agent to infer the boundary.

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 statement of when to use this tool versus alternatives, no preconditions, and no exclusions. The only directive content is the pricing note about free trial calls, which does not help an agent decide between this and the many adjacent physics/unit tools.

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