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

Annotations already declare read-only and idempotent, and the description adds meaningful behavior: the month-inclusive/exclusive convention, the conditional outputs, and the instruction to pull raw indices when `incluir_valores` is set. No contradiction exists.

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 dense sentences pack purpose, date convention, and conditional modes without padding. The front-loading of the core operation makes the primary action clear immediately.

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 read-only query with no output schema, the description covers the main return types (corrected value, monthly variations) and the critical date convention. The absence of `pro_rata` semantics and an explicit output example leave minor gaps, but the core call pattern is well-specified.

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%, so the description must carry parameter meaning. It explicitly explains `valor` and `incluir_valores`, and implicitly covers `data_inicial`/`data_final` through the 'between two dates' phrasing and month convention. However, `pro_rata` is never mentioned, and the `indice` enum is only referenced generically as 'índice oficial', leaving a gap for a tool with six parameters.

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 specifies a concrete operation: querying an official index's accumulated correction factor between two dates, with the BACEN/IBGE month convention. It also clarifies two result modes (corrected value or monthly variations), which distinguishes it from sibling calculation tools that target specific subjects like FGTS or aluguel. Though it does not name a sibling, the resource and operation are unambiguous.

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?

The description explains conditional behavior — when `valor` is supplied it returns the corrected amount, and when `incluir_valores` is true it returns raw monthly changes — which guides invocation parameter usage. However, it does not explicitly state when to choose this tool over alternatives or when not to use it. The guidance is implied by the domain rather than stated.

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