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

With no annotations supplied, the description carries the full behavioral burden. It helpfully discloses the commercial model ('5 free trial calls per signed wallet'), but says nothing about return shape (single number vs. series), error behavior on too-short input, or whether period bounds are enforced.

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 compact sentences, front-loaded with the verb and resource, then parameters, then the pricing caveat. Nothing is redundant and nothing obscures the core purpose.

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 two-input calculator with no output schema, the definition covers purpose, inputs and the billing constraint adequately. The remaining gaps, chiefly the serialization format of 'values' and the minimum data requirement, are real but modest for a tool of this complexity.

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 0% and both parameters are untyped strings with no field descriptions, so the description must compensate. It adds the meaningful default (period 14) and identifies 'values' as the price series, but never states the expected encoding of 'values' (comma-separated string vs. JSON array), which is the key ambiguity given the string type.

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 uses a specific verb and resource ('Calculate the Relative Strength Index (RSI) of a price series') and spells out the acronym, which cleanly separates it from sibling indicators such as x402-sma, x402-ema, x402-macd and x402-williams-r. It stops short of saying what makes RSI the right indicator versus those alternatives.

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?

Usage is only implied: an agent can infer this is for a numeric price series, and it learns 'values' plus an optional 'period' defaulting to 14. There is no statement of prerequisites, minimum series length needed for a valid RSI, or when to prefer this over other momentum tools.

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