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

With no annotations, the description carries the full burden of behavioral disclosure. It states nothing about read-only nature, output format, timezone handling, or error conditions—all critical for a time-related utility.

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?

The description is extremely short and front-loaded, but its brevity comes at the cost of under-specification. It is concise but not sufficiently informative.

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?

Given no annotations, no output schema, and a minimal one-parameter schema, the description is completely inadequate. It fails to explain what 'elapsed time' means, how the result is formatted, or any edge cases, leaving the agent unable to call the tool confidently.

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 100%, so the schema already documents the single 'start' parameter. The description adds no meaning beyond what the schema provides, but per rubric baseline 3 applies when coverage is high.

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 'Elapsed Time: Elapsed time between two moments' restates the name and title without adding a specific verb or resource. It is essentially a tautology of the tool name x402-elapsed-time, giving no more information than the name itself already conveys.

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 indication of when to use this tool versus alternatives. Siblings like x402-time-ago, x402-seconds-to-human, or x402-duration exist, but the description offers no differentiation or guidance on selection.

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