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

With no annotations, the description carries the full burden. It does disclose real behavioral facts: the result is an absolute (order-independent) difference, the output is expressed in days and hours, and there is a '5 free trial calls per signed wallet' quota. It omits any statement about date-format tolerance, partial-day handling, or timezone behavior.

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?

A single front-loaded sentence states the operation, its ordering semantics and its output units with little waste. The trailing '🆓 5 free trial calls per signed wallet' tag is promotional but conveys a real quota constraint.

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 simple two-param computation with no annotations and no output schema, the description covers the output shape ('days and hours') and the result semantics, but leaves the input date format unspecified and does not route away from the many overlapping date/time siblings.

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?

Schema description coverage is 0% for both parameters, so the description must compensate and largely does not. It names 'start' and 'end' dates, which maps to the schema keys, but gives no accepted format (ISO 8601 string? unix timestamp?) for either, leaving the agent to guess the input syntax.

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?

Names a specific verb and resource ('Returns the absolute difference between start and end dates') and even specifies the output units (days and hours). It does not distinguish itself from close siblings such as x402-date-diff or x402-hours-between, so an agent cannot tell them apart from the text alone.

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 and no alternatives are named, despite several near-duplicate siblings (x402-date-diff, x402-hours-between, x402-days-since, x402-days-until). The agent is left to infer that this is the correct pick for a date-span computation.

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