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

No annotations are supplied, so the description carries the full behavioral burden and mostly does not: nothing is said about the expected timestamp format, whether 'start' defaults to now, or what unit/format the elapsed value is returned in. The one genuine disclosure is the commercial constraint ('5 free trial calls per signed wallet'), which is useful but tangential to correct invocation.

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?

It is short and the purpose leads, but the opening 'Elapsed Time: Elapsed time...' redundantly restates the name, and the trial-call marketing line occupies space that could have carried input-format 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?

With no annotations, no output schema, and 0% parameter documentation, the description would need to explain input format and return semantics for an agent to call this reliably. It explains neither, and the mismatch between 'two moments' and a single 'start' parameter is left unresolved.

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 the single 'start' parameter, and the description never mentions it or its accepted formats (ISO 8601, Unix epoch, relative string). 'Two moments' hints that a second time exists but does not explain how it is supplied, leaving the parameter essentially undocumented.

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 names a concrete operation ('elapsed time between two moments'), which is more than a restatement of the name, but it is imprecise: the schema exposes only a 'start' input, so it is unclear what the second moment is (now? a default?). It also does nothing to separate itself from the many nearby time siblings such as x402-duration, x402-days-between, or x402-time-ago.

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 exclusion of alternatives, and no indication of how this differs from the numerous other interval/duration tools in the sibling list. The only extra sentence is a pricing note, not usage guidance.

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