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

With no annotations, the description carries the full behavioral burden. It implies a pure, read-only calculation (no mutation risk), which is the main behavioral concern, but it does not describe the returned value, units, or how the period affects output. For a stateless calculator the missing pieces are modest, so a mid score is appropriate.

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, front-loaded with the indicator definition, followed by the invocation inputs. No filler or redundancy; every clause carries information.

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 stateless calculation with no output schema and no annotations, so little is required. The description gives enough to call it correctly (arrays plus optional period). It leaves the 'values' parameter unexplained, which is a small completeness gap.

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 nominally 100%, but the schema descriptions are trivial ('High to process', 'Period to process'). The description adds real meaning: it identifies low/high/close as price arrays and supplies the default period value of 14, which is absent from the schema. It does not mention the 'values' parameter, a minor omission.

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 and resource: 'Calculate Average True Range (ATR), a volatility indicator.' This lets an agent distinguish it from sibling indicator tools like x402-sma, x402-ema, x402-rsi, and x402-macd by the named indicator. It stops short of explicitly contrasting with those siblings, so it is clear but not sibling-differentiated.

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?

It explains how to invoke (supply high/low/close arrays, optional period) but never states when to prefer ATR over the many other volatility/indicator siblings such as x402-stddev or x402-bollinger-bands. There is no when-to-use or when-not-to-use guidance, only a restatement of inputs.

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