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

With no annotations, the description carries the full transparency burden. It discloses the core behavior — a pure predicate returning true for non-integer numbers — which is adequate for a simple check. However, it leaves edge cases (NaN, Infinity, exponential notation, numeric strings) unexplained, and the instruction to 'Provide value' sits uneasily against a schema that declares no input mechanism.

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 two sentences with the core check front-loaded ahead of the return contract. Minor waste exists — the 'Is Float:' prefix repeats the tool name, and 'non-integer numbers' partly re-states the parenthetical — but overall it is compact and every remaining clause earns its place.

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?

No output schema exists, so the description must cover return values, and it does ('returns true for non-integer numbers'). But neither annotations nor an input schema exist, and the description fails to explain how the value is passed to the tool despite instructing 'Provide value'. For a trivial predicate, the definition should be fully self-sufficient; the unresolved input mechanism is a fundamental completeness gap.

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?

With 0 parameters, the baseline is 4, and the description does add meaning by defining what counts as a float ('has a fractional part', 'non-integer). But it conflicts with the schema: the empty properties object gives an agent no place to supply the value the description demands. The description adds semantics but fails to resolve the invocation contract, so it does not earn the full baseline.

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 verb and resource — 'Check whether a value is a float' — and reinforces the semantic with two operative glosses: 'has a fractional part' and 'returns true for non-integer numbers'. This is specific enough for an agent to understand the predicate, and the non-integer framing implicitly distinguishes it from sibling tools like x402-is-integer, though no sibling is named explicitly.

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. 'Provide value' is an invocation instruction, not a usage guideline, and nothing explains when this tool is preferable to the many is-* siblings (x402-is-integer, x402-is-numeric). With such a large sibling list, explicit routing would be cheap and valuable, but it is absent.

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