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. 'Format a duration in human terms' essentially restates the tool name and reveals nothing about accepted input formats, output conventions, edge-case handling, or whether the operation has side effects. With zero annotation coverage, this is a significant gap.

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 eight-word sentence that is front-loaded with the purpose and contains no filler. It is efficient for what it carries, though the terseness comes at the cost of the guidance and behavioral context that other dimensions penalize.

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 formatting tool this might be nearly adequate, but the context makes it insufficient: there are multiple sibling tools with overlapping names, there is no output schema to describe the return value, and there are no annotations to convey the read-only safety profile. The description does nothing to disambiguate, specify input units, or characterize the output, so an agent cannot confidently select and invoke it.

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 baseline is 3. Each parameter has a nominal description ('Ms to process', 'Value to process', 'Milliseconds to process'), but these are generic and give no clue that the three strings appear to be aliases for the same quantity. The tool description adds nothing about which parameter to prefer or how the value should be formatted — it neither improves nor harms the schema's weak semantics.

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 states a verb ('Format') and a resource ('a duration'), so it is not a tautology. However, 'human terms' is vague — it doesn't specify the output style (e.g., '2 hours 30 minutes' vs '2.5h'), and it fails to distinguish this tool from near-identical siblings like x402-duration-humanize and x402-duration, which an agent would reasonably consider equivalent.

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?

No guidance is given on when to use this tool versus the several overlapping alternatives (x402-duration-humanize, x402-duration, x402-seconds-to-human). No context, exclusions, or alternative names are mentioned, leaving the agent to guess which sibling satisfies a 'humanize a duration' request.

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