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 fails completely. The text reveals nothing about units, sign conventions, whether the difference is absolute, inclusive/exclusive boundary handling, or timezone behavior. For a date computation tool these are consequential unknowns.

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?

Four words with two unique tokens is not conciseness but under-specification. The text is aggressively short yet conveys no operational information, so it fails the 'every sentence should earn its place' test in the opposite direction.

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 tool has no annotations, no output schema, an empty input schema, and a two-word tautological description. An agent cannot determine how to invoke it (what dates to provide, and how), what unit the difference is returned in, or what edge cases apply. For a date arithmetic tool this is completely inadequate.

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 schema coverage is 100% (vacuously), so there is no parameter documentation gap for the description to fill. Per the baseline rule for zero-parameter tools, a 4 is appropriate. The suspicion that a date-diff tool with an empty input schema is malformed belongs to contextual completeness, not this dimension.

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 'Date Diff: Date Diff' is a pure tautology that restates the tool name without any verb+resource explanation. It does not state what inputs the tool accepts, what computation is performed, or what unit the result is expressed in. The name hints at the purpose, but the description itself adds zero informational content.

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 provides no guidance whatsoever about when to use this tool versus its many date/time siblings such as x402-days-between, x402-hours-between, x402-weekdays-between, x402-date-math, x402-duration, or x402-elapsed-time. An agent is given no basis for selecting x402-date-diff over these alternatives.

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