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

No annotations are supplied, so the description carries the full burden. It does disclose one useful behavioral fact not present in structured data — the pay-per-call model with a 5-call free trial per signed wallet — but says nothing about required units, default assumptions (e.g. Earth mass/radius), precision, or what the response looks like.

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?

Short and front-loaded, but the first sentence is pure redundancy with the tool name. The pricing line is the only sentence carrying new information; nothing is bloated, but almost nothing earns its place either.

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?

With no annotations, no output schema, no required-parameter flags, and zero schema coverage, this definition leaves every practical question unanswered: units, defaults, return value, and failure modes. For a two-parameter physics calculator the description is inadequate.

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% for both parameters, so the description must compensate and does not. It never mentions mass or radius, let alone whether values are SI (kg, meters), scientific notation, or accept named bodies — despite both being typed only as unconstrained strings.

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?

"Escape Velocity: Velocity of escape" restates the tool name in slightly different words and never states that it computes a physics quantity from a mass and a radius. An agent can guess the domain but not the operation or the formula. It also fails to distinguish itself from neighbors such as x402-velocity, x402-angular-velocity, or x402-orbital-style tools.

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 use this rather than x402-velocity or the related physics calculators (x402-earth-mass, x402-earth-radius, x402-gravitational-constant). The only extra sentence covers billing ("5 free trial calls per signed wallet"), which is not usage selection guidance.

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