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

With no annotations, the description carries the full burden and does add useful behavior: the period default of 14, the flat-window edge case (emits -50 instead of dividing by zero), and a paywall/quota signal (5 free trial calls per signed wallet). It still omits output shape (single value vs array) and any input-format behavior, so it is partial disclosure rather than complete.

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?

One front-loaded sentence that puts the algorithm first, then input, default and edge case. The emoji + trial-call promo is promotional noise rather than definitional content, which keeps it out of 5.

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 two-parameter, no-annotation, no-output-schema tool, the description covers the what and the default but not the input encoding or the return shape, which the agent must guess. Adequate but with clear gaps.

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 coverage is 0% and both parameters are typed only as generic strings, so the description must compensate; it does identify that 'values' is an array and that 'period' defaults to 14. It never specifies the accepted encoding for that array (comma-separated, JSON) nor units/limits on period, leaving a real gap.

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?

States a specific verb (computes), named resource (Williams %R), its input (a values array) and default (period 14), so the agent knows exactly what it gets. It does not, however, distinguish itself from sibling indicator tools like x402-rsi, x402-stochastic or x402-macd, so it falls short of 5.

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 mention of when Williams %R is preferred over the sibling oscillators (RSI, stochastic), and no exclusions. The default period is the only operational hint, which is not usage guidance.

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