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 a billing/rate constraint (5 free trial calls per signed wallet), which is genuinely useful context, but says nothing about how the input must be formatted, whether computation is pure/local, error behavior, or what the response contains. For a zero-annotation tool this leaves the core behavioral picture incomplete.

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?

Front-loaded with the tool name and definition, then the pricing note; no filler sentences. The emoji and trial-call clause are somewhat marketing-flavored but short and arguably informative. Efficient overall.

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, and an undocumented single parameter, the description should do more: the input encoding and the return shape (a single number, presumably) are unstated. It covers the concept and the formula but leaves the operational details an agent needs to invoke it correctly.

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?

There is one parameter ('values') with 0% schema description coverage, so the description must compensate. The formula 'sum of squared relative frequencies' hints that the input is a set of frequencies, but it never states the encoding — comma-separated string, JSON array, whitespace-delimited — which is critical since the schema types it as a bare string. Partial compensation only.

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 ('Computes the Simpson diversity index') and even gives the formula ('sum of squared relative frequencies'), which implicitly distinguishes it from the sibling x402-simpsons-rule (numerical integration). It does not, however, name or contrast itself against related siblings such as x402-shannon-entropy or x402-gini-coefficient, so an agent must infer the boundary itself.

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 offers no when-to-use guidance, no preconditions, and no alternatives; it only states what the tool computes. The '5 free trial calls per signed wallet' note is commercial/pricing information, not usage guidance for selecting this tool.

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