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 completely fails. It does not state what input the tool accepts, what it returns, whether it mutates state, or how data is passed given there are no parameters. With an empty input schema, the description needed to explain the invocation contract (e.g., pipeline input, implicit context) and says nothing.

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?

At four words, the description is short, but this is under-specification rather than concise writing. Every word is wasted on restating the name; no sentence earns its place because no information is conveyed. A genuinely concise description would say what the tool does in a single informative sentence.

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?

The definition is completely inadequate for a tool with no annotations, no output schema, and an empty input schema. An agent cannot determine how to invoke the tool, what data it operates on, or what result to expect. Even one sentence ('Sorts the supplied array of numbers using heap sort, returning the sorted array') would resolve the fundamental ambiguity, but none is present.

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?

The input schema has 0 parameters, which per the calibration baseline warrants a 4 since there is nothing the description must document about parameters. The schema's emptiness is itself a red flag—an agent is left wondering how the tool receives data—but that gap is a behavioral/contextual issue rather than a parameter-documentation deficit. The description adds no parameter meaning, yet none is strictly required with zero declared parameters.

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 'Heap Sort: Heap Sort' is a pure tautology—it restates the tool name with no added content. It fails to state a verb, resource, input, or output, and provides no differentiation from the many sibling sorting tools (x402-bubble-sort, x402-quick-sort, x402-merge-sort, etc.). An agent learns nothing it couldn't already infer from the name.

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 guidance is provided on when to use this tool versus alternatives. Given the large family of sort tools among siblings, the description should at least mention heap sort's profile (e.g., O(n log n) worst-case) or note when another sort is preferable. There is no misleading guidance, but there is zero actionable usage direction.

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