get_ptax_latest

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

There are no annotations, so the description carries the full behavioral transparency burden. It correctly communicates that this is an official, closing, read-only rate lookup. Yet it does not mention edge cases such as no published rate within the lookback window, weekend/holiday behavior, or the expected output format.

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 a single, front-loaded sentence that conveys the action, the target resource, the official nature of the rate, the currency pair, and the authoritative source. There is no redundant or extraneous wording.

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 simple optional-one-parameter tool with high schema coverage, the description gives enough clarity about what the tool returns and its source. The main gap is the absence of return format details and edge-case behavior, which would matter more for a more complex tool.

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 covers 100% of the single parameter with a clear description, including default, maximum, and exclusive minimum. The tool description itself does not need to add parameter details because the schema already does the necessary work, supporting the baseline score of 3.

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 uses a specific verb and resource: 'Get the most recent official closing USD/BRL PTAX exchange rate' and identifies the source (Banco Central do Brasil). The word 'latest' clearly implies the tool's scope compared to date/period siblings. It stops short of explicitly naming the sibling tools, so it does not fully distinguish itself in the description itself.

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 implies when to use this tool: when the most recent PTAX rate is needed. However, it does not explicitly state when not to use it or mention alternatives like get_ptax_by_date or get_ptax_by_period. The agent must infer the selection logic from the tool name and context.

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