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

With no annotations, the description carries the full behavioral burden and does well: it discloses the exact computation, the normalization step (lowercasing), and the empty-input return value (0). It also hints at the payment/trial model. It stops short of stating auth requirements, rate limits, or error behavior.

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 metric definition is front-loaded in a single efficient sentence with no wasted prose. The trailing emoji and free-trial note are promotional padding that doesn't aid invocation, keeping it just short of a 5.

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 text metric with no annotations and no output schema, the return semantics are well specified. However, the unexplained dual parameters ('text' vs 'input') are a real completeness gap that the description does not resolve.

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% and there are two string parameters ('text' and 'input') whose relationship is undefined and not required. The description mentions 'empty text', hinting at the 'text' param, but never explains what 'input' is or whether the two are alternatives, leaving genuine ambiguity for the caller.

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 states a specific operation (compute the ratio of unique whitespace-separated words to total words after lowercasing) with the exact formula and the empty-text edge case. This is precise enough to distinguish it from near siblings like x402-char-diversity, x402-word-count, or x402-type-token-ratio without opening any schema.

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?

Usage is implied by the precise metric definition, so an agent can infer when it applies, but no alternative tools are named and no when-not guidance is given. The only extra context is a payment note ('5 free trial calls per signed wallet'), which is not usage routing.

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