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

With no annotations, the description carries the full burden and mostly fails: it discloses only a pricing/auth hint ("5 free trial calls per signed wallet"). It says nothing about what happens after the free calls, what the return value looks like, or whether the operation is read-only, leaving the agent to guess at a metered/paywalled call.

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?

It is short and front-loads the tool name, but the text is two fragments rather than a coherent sentence, and the emoji-flagged pricing line occupies a third of the description without helping an agent invoke the tool.

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 simple calculator the bar is low, but with no output schema, zero parameter documentation, ambiguous string inputs, and an unmentioned sibling duplicate, an agent still lacks the information needed to call this correctly or to prefer it over x402-discount-calc.

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?

Two parameters (price, discount) have 0% schema description coverage, and the description never mentions them at all. Since both are typed as strings, an agent cannot tell whether "discount" expects "15", "15%", or "0.15" — a format ambiguity the description should have resolved and does not.

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?

"Discount and percentage calculators" restates the tool name as a vague category rather than stating a specific operation; it never says whether it computes the discounted price, the savings amount, or a percentage. There is also a near-identical sibling, x402-discount-calc, that the description does nothing to distinguish from this one.

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?

No when-to-use guidance, no prerequisites, and no mention of alternatives despite several near-neighbours (x402-discount-calc, x402-percent, x402-percent-of, x402-percentage-change). The only extra sentence concerns free-trial credits, which is billing information rather than selection guidance.

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