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

No annotations are provided, so the description carries the full burden of behavioral disclosure, and it says nothing about behavior, side effects, input expectations, or return values. 'Difference' is ambiguous — set difference, array difference, or numeric difference — and the description does not resolve it. The behavioral profile is completely empty.

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 text is short, but this is under-specification rather than conciseness — the single sentence carries no information and does not earn its place. Per the calibration rubric, a vacuous stub on this dimension scores 2.

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, an empty schema, no output schema, and a tautological description, the text is the agent's only source of guidance and it explains none of the tool's inputs, outputs, or semantics. An agent cannot determine what operands to provide, what result to expect, or which of the many difference-related siblings to choose. This is completely inadequate given the absence of all structured metadata.

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 tool has 0 parameters and the schema trivially covers 100% of them, so the 0-param baseline of 4 applies: there are no parameter semantics the description needed to document. The description adds no meaning, but there is no parameter gap in the schema for it to fill. An agent is not misled about arguments because the schema correctly states there are none.

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 'Difference: Difference' is a pure tautology that restates the tool name without providing any verb, resource, or operation semantics. It gives no basis to distinguish this tool from siblings such as x402-symmetric-difference, x402-diff-array, or x402-json-diff. This mirrors the calibration example where a name-restating stub 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 statement of when to use this tool or when to prefer an alternative. Among a large field of plausible siblings (x402-diff-array, x402-json-diff, x402-text-diff, x402-symmetric-difference), none are referenced. An agent receives zero selection guidance.

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