bcb_cambio_cotacao

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

Annotations already declare readOnlyHint, openWorldHint, idempotentHint, and destructiveHint=false, so the read-only profile is clear. The description adds substantial behavioral context: the default 7-day window, business-day-only quotes, Refinitiv coverage for non-USD parities, BCB disclaimer passthrough, and the origin of the data. This goes well beyond the annotations.

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 description is longer than minimal, but it is well structured with clear sections: purpose, when to use, when not to use, return fields, source, and caveats. It is front-loaded and organized enough to scan, although the return field list is partially redundant given the existing output schema.

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 5-parameter read-only query tool with a rich output schema and strong annotations, this description is complete enough. It covers default behavior, business-day limitations, the meaning of the data, the external source of non-USD parities, and when a sibling tool should be used instead.

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 input schema already has 100% parameter coverage with defaults, constraints, and format examples, so the baseline is 3. The description reinforces the default 7-day window and day-versus-range distinction, but most of that is already expressed in the schema; the description adds only modest contextual color for 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 opens with a precise action ('Consulta a cotação PTAX de uma moeda contra o real') and clearly states the supported scope: a specific day or a date range. It also differentiates from siblings explicitly by naming bcb_serie_valores for long SGS series and bcb_cambio_moedas for currency symbol lookup.

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 contains an explicit 'Quando usar' and 'Quando NÃO usar' section. It tells the agent exactly when to prefer this tool and when to use alternatives, including the specific SGS series codes for dollar—which is unusually clear guidance.

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