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

No annotations exist, so the description carries the full burden of behavioral disclosure. It conveys the happy-path calculation and the default period, but it fails to disclose the minimum data length (period+1 values), what happens with insufficient or zero values (division by zero), whether the output is a single value or an array aligned to input, or how the percentage is scaled. For a calculation tool 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?

Two sentences with no wasted words; the core verb and calculation are front-loaded before the input instruction. The 'Roc:' prefix slightly redundantly echoes the tool name, but overall the description is efficient and scannable.

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, an empty input schema, and no output schema, the description must carry the full call contract, but it only states the high-level calculation. An agent lacks the formula (ROC = (V_t - V_{t-period}) / V_{t-period} * 100), the minimum length requirement, edge-case behavior, and the response shape. For a simple indicator tool this is inadequle.

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 description is the only source of parameter information because the schema's properties object is empty, and it does mention a values array and optional period with default 12. However, it directly contradicts the schema, which declares zero parameters, so an agent cannot tell whether to pass structured arguments at all. It also omits element type for the values array and any meaning of 'period''. The 0-param baseline of 4 is undermined by this schema-description mismatch and thin detail.

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 specific verb (calculate), a resource (Rate of Change), an output format (percentage), and a scoping parameter (period). It also usefully disambiguates the ambiguous acronym 'ROC' as 'Rate of Change' rather than 'Return on Capital'. However, it does not differentiate itself from the near-duplicate sibling x402-rate-of-change or the related x402-momentum, so it stops short of full sibling distinction.

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 select this tool over alternatives such as x402-rate-of-change, x402-momentum, or x402-percent-change-array. The description only states input requirements ('Provide values array and optional period') with no context about use cases, exclusions, or preferred alternatives, leaving selection entirely to inference.

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