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 does not state what input format is expected (ISO 8601, seconds string, milliseconds), what output format is produced (e.g., '2 hours 3 minutes' vs '2h 3m'), whether zero or negative durations are handled, or what localization/unit conventions are used. The behavior after calling the tool remains ambiguous.

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, which keeps it free of fluff, but it is under-specified rather than efficiently informative. It front-loads the main verb but omits essential operational details, so the brevity works against usefulness.

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?

This is a simple tool, but the description is incomplete for reliable selection and invocation. There are no annotations or output schema, there are three ambiguous optional parameters, and the description doesn't differentiate it from multiple closely named siblings. An agent cannot confidently know what input to send or what response to expect.

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 schema describes three parameters ('value', 'seconds', 'duration') with placeholder-like descriptions ('Value to process', 'Seconds to process', 'Duration to process'), which adds almost no meaning. The tool description does not clarify whether these are alternatives, which one is preferred, or what formats each expects. With 0 required parameters, an agent has no guidance on how to construct a valid invocation.

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 'Duration Humanize: Humanize a duration.' uses a verb and a resource, so it states the basic purpose. However, it is largely tautological — essentially restating the tool name and title. It also does not explain what 'humanize' means, e.g., converting seconds into a readable string like '1h 2m 3s', and it does not distinguish itself from siblings like x402-duration, x402-duration-human, x402-seconds-to-human, or x402-relative-time.

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 guidance on when to use this tool versus alternatives. Multiple sibling tools have similar duration-related names (x402-duration, x402-duration-human, x402-seconds-to-human, x402-relative-time). The description also doesn't clarify when to pass 'value' vs 'seconds' vs 'duration', or which of the three optional parameters should be supplied.

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