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

With no annotations, the description carries the full burden; it does disclose a real behavioral constraint (5 free trial calls per signed wallet), which is useful payment/authorization context. However it says nothing about the returned values (MACD line, signal line, histogram), failure modes for short or non-numeric input, or whether the call is idempotent/read-only — gaps that matter more because annotations are absent.

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?

Three short sentences with the definition and input instruction front-loaded; the free-trial note is marketing but does convey a call limit, so it earns some place. No redundancy or filler beyond that.

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 numeric computation tool with zero annotation coverage, zero schema description coverage, and no output schema. The description should therefore explain the input encoding, the standard period defaults, and the shape of the result (MACD/signal/histogram); it covers none of these, leaving the agent to guess the call contract.

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 all four parameters are untyped strings, so the schema supplies no meaning at all. The description only says 'provide values array and optional fast/slow/signal periods' — it never states the encoding for 'values' (comma-separated string vs JSON array), nor the default periods (conventionally 12/26/9) or valid ranges for fast/slow/signal, so an agent cannot reliably format a call.

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 gives a specific verb ('Calculate') plus the exact resource ('the MACD (Moving Average Convergence Divergence) indicator'), including the acronym expansion, so there is no ambiguity about what is computed. It does not name a sibling such as x402-ema or x402-sma to delineate when this indicator is preferred over them, which keeps it just below a 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?

Usage is implied: pass a series of values with optional fast/slow/signal periods to obtain MACD. There is no explicit 'use this instead of x402-ema/x402-sma/x402-rsi' routing, no statement of required data length (MACD needs enough observations for the slow period), and no mention of when not to use it.

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