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

With no annotations, the description carries the full burden. It usefully discloses the commercial model (x402 pay-per-use, 0.02 USDC on Base), which an agent needs before invoking, but says nothing about authentication, error cases, rate limits, or what the computation returns.

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 compact clauses, front-loaded with the purpose, then the input example, then the price tag. No padding, though the mix of Spanish and English framing is slightly inconsistent for a compact spec.

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 one-parameter tool with no output schema, the definition covers input syntax and cost but omits what comes back (a decimal? percent? over which window?) — a meaningful gap when the return value is the whole point of the tool.

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 schema declares the single parameter only as the generic "service input", so the description is what actually defines the interface: input='btc,30' (moneda,dias). That concretely conveys format, ordering, and the units (coin, days) an agent would otherwise have to guess.

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?

"Volatilidad histórica de una cripto" states the resource (crypto volatility, historical) specifically enough to separate it from siblings like crypto-price, precio-cripto or historial-precios, which return prices rather than a volatility metric. The verb is implied by the tool name rather than spelled out in the description, so it falls just short of 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?

No when-to-use guidance and no routing to alternatives: it never says how this differs from the many crypto/price tools in the sibling list (precio-cripto, crypto-price, historial-precios, trading-signal). The only context is the input format and cost, not applicability.

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