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

Annotations already declare readOnly, idempotent, non-destructive and closed-world, so the safety profile is covered. The description adds the fiscal-scope caveat and hints at the two returned quantities, but says nothing about what happens if the months are inverted or out of range, nor about error behavior.

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?

A single front-loaded sentence: verb, output, scope exclusion, then use cases. Dense but no wasted sentences; the parenthetical and colon chain make it slightly heavy to parse but it stays tight.

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 two-parameter, read-only calculation with full schema coverage and complete annotations, this is close to complete, especially since it names both returned quantities despite there being no output schema. The remaining gap is the unspecified behavior for invalid or inverted month ranges.

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 100% and both parameters already document the AAAA-MM format and the older/newer ordering. The description only says 'dos meses concretos' and adds no meaning beyond the schema, so the baseline of 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 (calcula) and resource (variación del INPC / inflación acumulada) and explicitly scopes itself against the fiscally-flavored sibling by saying it works 'sin las reglas fiscales del Art. 17-A'. An agent can distinguish it from calcular_factor_actualizacion_fiscal without opening either schema.

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?

Names concrete use cases (ajustar rentas, pensiones, contratos indexados) and implicitly excludes the fiscal-rule variant, which routes the agent to the sibling. It stops short of naming the alternative tool or stating an explicit when-not condition.

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