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

Annotations already declare readOnlyHint, idempotentHint, openWorldHint=false and destructiveHint=false, so the safety profile is covered; the description nonetheless adds genuine non-annotation detail: 12-significant-digit precision, exact definitional factors, and hard limits (64 KB input, 1 s per call, 1 MB result). It slightly restates annotation claims ("sin red, sin estado guardado"), which keeps it from a 5.

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?

The content is well front-loaded (units, then behavior, then when/not-for, then side effects), but the full Spanish block is followed by a near-identical English block plus a pointer to inputSchema.description, roughly doubling length without adding 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?

An output schema exists, so return-shape explanation is unnecessary; the description still covers units, default all-units behavior, precision, determinism, time/size limits and the sibling alternative. Nothing an agent needs in order to call it correctly is missing.

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 100%: units, required status and the "omit for all" behavior of `to` are already documented per-parameter. The description's "Sin 'to' devuelve todas" echoes the schema rather than extending it, so baseline 3 applies.

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 and resource ("Convierte tasa de datos entre unidades") and enumerates all supported units, including the bit vs byte vs binary distinction. It also names the sibling it must not be confused with (convert-data-size), so an agent can separate it from the long list of convert-* tools.

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?

Explicit "Cuándo:" clause defines the triggering condition (exact definitional unit conversion) and "No para:" names the alternative tool (convert-data-size) for data-size conversion. That covers when-to-use, when-not, and the alternative in one place.

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