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 delivers nothing: no input expectations, no output shape, no determinism or ordering notes. The only text present is the name repeated.

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?

Extremely short, but this is under-specification rather than conciseness — there is no front-loaded statement of purpose to compress. Two words separated by a colon carry zero information.

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 two-parameter tool with no annotations and no output schema, the description should at minimum define the operands and the operation. Nothing is supplied, leaving the agent unable to invoke the tool correctly.

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 schema nominally has 100% description coverage, but those descriptions ('A to process', 'B to process') are vacuous placeholders that convey no semantics. The description adds nothing further, so an agent cannot tell what a and b should contain (numbers? strings? arrays?) or what the ordering of the result means.

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 is 'Difference: Difference', a pure restatement of the tool name with no verb, resource, or operation described. It does not say whether this computes numeric subtraction, string diffing, or set difference, all of which exist as distinct siblings (x402-diff-array, x402-text-diff, x402-symmetric-difference, x402-json-diff).

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 when-to-use guidance, no mention of alternatives, and no conditions or prerequisites. The agent has no basis for choosing this over the many other diff/difference siblings.

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