cambio_dolar

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

With no annotations, the description carries full burden. It discloses the data source (BCB Olinda/PTAX), explains PTAX as official reference rate, and specifies behavior on weekends/holidays (returns last business day). This is good behavioral context, though rate limits or error handling are not mentioned.

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 two concise paragraphs. The first sentence states the primary purpose, followed by source and key behavioral note. The second paragraph lists return fields. No unnecessary words, and critical information is front-loaded.

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 parameterless tool with an output schema (present but not shown), the description fully explains what the tool does, its data source, behavior on non-business days, and the structure of the return value. No additional information seems necessary for correct usage.

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 tool has zero parameters and schema coverage is 100%. The description adds value by detailing the return fields (fonte, moeda_origem, compra, venda, etc.), which compensates for the absence of parameter documentation. Baseline for no parameters is 4.

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 clearly states the tool returns the official PTAX quotation for USD/BRL from Brazil's Central Bank. The verb 'retorna' (returns) and specific resource 'cotação PTAX oficial do dólar americano' leave no ambiguity. Sibling tools are all agricultural, so this currency tool is distinct.

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 explicit when-to-use or when-not-to-use guidance is provided. The description implies usage for obtaining official exchange rates, but does not mention alternatives or scenarios where other tools might be preferred. Given no similar tools among siblings, the lack is less critical but still a gap.

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