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

With no annotations provided, the description carries the full burden of behavioral disclosure, and it discloses nothing: no return format, no input expectation, no side effects, no example behavior. The agent cannot even determine whether this is a read-only predicate or something else.

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 description is short but this is under-specification, not conciseness. It repeats the name twice with a colon separator, earning no informational value per word. Every sentence should add meaning, and this one adds none.

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?

Even for a simple tool, the description is completely inadequate. With no annotations, no output schema, and an empty input schema, the description was the sole channel for operational information and it provides zero. An agent cannot correctly select or call this tool among thousands of similar siblings.

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?

Per the rubric, 0 parameters earns a baseline of 4, and the empty schema has 100% coverage, so there are no parameter semantics for the description to document. However, the empty schema itself is suspicious for a tool that must operate on some input, and the description does nothing to clarify how input is supplied.

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 'Starts With Vowel: Starts With Vowel' is a pure tautology that exactly restates the tool name 'x402-starts-with-vowel'. It provides no verb, no resource, and no distinction from any sibling tool. This matches the calibration example where a description identical to the name scores 1.

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 whatsoever about when to use this tool versus alternatives such as x402-ends-with-vowel, x402-is-vowel, or the hundreds of other predicate tools. An agent receives no context about the intended input type (string? word?) or invocation scenario.

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